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P A Lefevre

Publications and source records attributed to P A Lefevre.

At least 19 recordsLinked to original sources
PubMed2004

Testosterone-stimulated weanlings as an alternative to castrated male rats in the Hershberger anti-androgen assay.

We showed previously that stimulation of weanling male rats with the synthetic androgen 17-methyltestosterone (17MT) caused premature growth of the sex accessory tissues such that the activity of the two anti-androgens flutamide and DDE could be demonstrated (Regul. Toxicol. Pharmacol. 35 (2002) 280). We suggested that that protocol should be evaluated as an alternative to the castrated male rat Hershberger assay. In the present paper we justify changing the assay protocol to use testosterone propionate (TP), in place of 17MT, as the stimulating androgen. This change enables biochemical formation of dihydrotestosterone from testosterone, a conversion not possible when using 17MT. This change in the protocol enables detection of the testosterone-5-reductase inhibitor finasteride. The modified TP-stimulated weanling male rat assay is shown to have similar sensitivity to that of the castrated male rat Hershberger assay in detection of the anti-androgens flutamide, procymidone, vinclozolin, and DDE, and of the biochemical inhibitor finasteride. The anti-androgen linuron and the anabolic steroid trenbolone were also detected as positive by the TP-stimulated weanling male assay. It is suggested that this modified assay for anti-androgens should be validated as an alternative to the Hershberger assay, thereby reducing animal stress by obviating the need for surgical castration.

Androgen Antagonists↗
PubMed2003

The effect on sperm production in adult Sprague-Dawley rats exposed by gavage to bisphenol A between postnatal days 91-97.

M. Sakaue et al. (2001,J. Occup. Health vol. 43, pp. 185-190) have described how oral exposure of sexually mature male rats to bisphenol A (BPA) between postnatal days (PND) 91-97 led to a reduction in daily sperm production (DSP) 5 weeks later (18 weeks of age). Activity was observed over the dose range 20 microgram/kg-200 mg/kg BPA, with an absence of activity over the dose range 2 ng/kg-2 microgram/kg BPA. There was no evidence of a dose response relationship over the active dose range (five orders of magnitude range). The observation of endocrine disruption (ED) effects for BPA at such low doses, and in sexually mature animals, was unexpected. It was therefore decided to mount an independent repeat of their study. A total of four independent studies were conducted according to the protocol used by Sakaue et al. Doses of 20 microgram/kg, 2 mg/kg, or 200 mg/kg BPA were administered to adult Sprague-Dawley (SD) rats over PND 91-97, and the studies were terminated when the rats reached the age of 18 weeks. Three different rodent diets were employed (RM3, Purina 5002, and CE2), the last of which had been used by Sakaue et al. BPA failed to give any evidence of ED activities, including the changes in DSP reported by Sakaue et al. 2001. During the course of these studies, the test protocol was adapted to coincide more precisely with that used by Sakaue et al.; this included restricting the number of animals per cage, removing bedding from the cages, and changing to the use of glass water bottles in the cages. The only thing of interest to emerge from our studies was the observation of a significant difference in DSP between the control groups of our first and second study. As the change in diet from RM3 to Purina 5002 was the major difference between those two studies, we conducted a repeat of the second study, but we were unable to confirm the differences seen between the first and second study. The probability that those differences arose either by chance, or as the result of intrinsic study-to-study variability, was strengthened by the absence of significant differences in the sperm parameters in a final (fifth) study where the sperm parameters for control animals maintained on the three different diets were compared under the conditions of the main experiments. No explanation for our failure to replicate the effects reported by Sakaue et al. is evident. A review of DSP values reported in the recent literature is provided and discussed, and it is concluded that use of the term DSP/g testis rather than DSP/testis could increase the sensitivity of DSP assessments.

Animals↗
PubMed2003

Comparison of prostate gene expression and tissue weight changes as monitors of antiandrogen activity in GNRH-inhibited rats.

BACKGROUND: The Hershberger assay for antiandrogens and modifiers of steroid biosynthesis uses surgically-castrated rats. We described an adaptation of the assay using the GnRH inhibitor Antarelix in place of surgical castration [Ashby J, Lefevre PA, Deghenghi R, Wallis N. Regulatory Toxicology and Pharmacology 34:188-203, 2001], and concomitantly described changes in expression of the androgen-dependent prostatic genes PBP C3, TRPM-2, and ODC as a possible complement to gravimetric analysis of the sex accessory tissues (SAT) [Nellemann C, Vinggaard AM, Dalgaard M, Hossaini A, Larsen J-J. Toxicology 163:29-38, 2001. METHODS: The present study describes the results of combining these two modifications into a single assay. During the course of these experiments it was shown that SD rats gave similar results to AP rats and that the higher stimulatory dose of testosterone propionate (TP) used in our experiments gave stronger assay responses to FLU than the lower dose of TP used by some earlier investigators. The potent antiandrogen flutamide (FLU) and the weak antiandrogen DDE were used to evaluate this modified assay. RESULTS: For all parameters studied (SAT weights and changes in expression of the 3 prostatic genes) FLU gave the expected positive results. The weak antiandrogen DDE gave variable and mainly non-reproducible responses. Use of DDE as a weak antiandrogen accelerated assessment of the new assay. CONCLUSIONS: Possible reasons for this failure to detect DDE are discussed, and it is concluded that the modified assay is unsuitable for use in its present form. The use of gene expression analyses together with evaluation of SAT weights is a promising tool as an early and sensitive marker of antiandrogen action, but more work is needed on the choice of time frame as well as the selection of genes to monitor.

Androgen Antagonists↗
PubMed2002

Concept evaluation: androgen-stimulated immature intact male rats as an assay for antiandrogens.

The effects of the concomitant oral administration of a potent reference androgen (17alpha-methyltestosterone) and both a potent (flutamide) and a weak (p,p'-DDE) antiandrogen on intact weanling male rats are described. This protocol resulted in the inhibition by the antiandrogens of the increase in sex accessory tissue weights induced by coadministration of 17alpha-methyltestosterone. Although both flutamide and p,p'-DDE inhibited the androgen-induced growth of the levator ani/bulbocavernosus muscle complex, the Cowper's glands, and the seminal vesicles, the growth of the prostate gland was unaffected by either antiandrogen. The unresponsiveness of the prostate gland, a primary target tissue in the castrated rat antiandrogen assay, has yet to be fully explained. However, the ability of the assay to detect the activity of low dose levels of the weak antiandrogen DDE (at doses of 20 mg/kg body weight) makes the system worthy of further study as one of several alternatives. Given the rapid rate of assay/protocol exploration and refinement of this assay and its alternatives, there is the need for careful comparative studies before selecting a single bioassay for validation and regulatory use.

Administration, Oral↗
PubMed2002

Comparison of the developmental and reproductive toxicity of diethylstilbestrol administered to rats in utero, lactationally, preweaning, or postweaning.

The objective of the study was to determine which period of exposure produces the most marked effects on the reproductive capacity and sexual development of the rat, with particular emphasis on the relative sensitivity of in utero and postnatal exposures. The endocrine active chemical, diethylstilbestrol (DES) was used as an agent known to affect many of the endpoints examined. Hitherto, such comparisons have been made between studies, rather than within a study. Our data will be helpful in the interpretation of future multigenerational assay data. In preliminary studies, DES was shown to be active in the immature rat uterotrophic assay with a lowest detected dose of 0.05 mg DES/kg body weight by sc injection and 10 mg DES/l (1.6 mg DES/kg body weight) by administration in drinking water. A dose of 60 microg DES/l drinking water ( approximately 6.5mg DES/kg body weight/day) was selected for the main study since this represented the midpoint of the drinking water uterotrophic dose response and produced no overt maternal toxicity. The study used 10 groups of concomitantly pregnant animals, including 2 control groups. The first comparison was between the effects of exposure to DES in utero, and exposure from conception to weaning. Another group of animals was exposed to DES in utero and cross-fostered to untreated pregnant females to prevent lactational transfer of DES to pups. Two groups were exposed to DES neonatally, either from birth to postnatal day (PND) 10 (pups thus having only lactational exposure), or from birth until weaning (PND 21; pups thus having both lactational exposure and self-exposure via drinking water). In addition, a dose response study to DES was conducted on animals exposed from weaning to PND 100, when the first phase of the study was terminated. Pups exposed to DES in utero and pups exposed from weaning to PND 100 were bred to assess fertility of the F1 animals and the sexual development of F2 offspring. This last comparison was to determine the extent to which weanling rats could be used in endocrine toxicity studies to assess their potential to show activity in utero. The most sensitive period of exposure for inducing developmental effects in F1 animals was from weaning onwards. The neonatal to weaning period (PND 1-21) was the next most sensitive. Essentially no effects were induced in F1 animals exposed in utero. No effects of any kind were observed in animals only exposed over the early neonatal period of PND 1-10. The mean day of vaginal opening, testes descent, and prepuce separation was only altered in groups where postnatal exposure to DES continued beyond PND 10, or was started at weaning. No changes were observed in anogenital distance or caudal sperm counts. Some changes in organ weights were observed, but the interpretation of these was often confused by concomitant changes in body weight. In general, histopathological examination of tissues yielded no additional information. In breeding studies with animals exposed to DES in utero, or from weaning, reduced litter sizes and marginal advances in the day of vaginal opening were observed in the offspring, together with changes in organ weights. However, no unique sensitivity was noted for exposure in utero. Evaluation of the several exposure periods and the many markers monitored in this study may have individual strengths in individual cases, but when rigorously compared using the reference estrogen DES, many preconceptions regarding their absolute or relative value were not upheld. Further, each of these markers is subject to natural variability, as demonstrated by comparisons made among the 5 separate control groups available in parts of the present study. This variability increases the chance that small changes observed in endocrine toxicity studies employing small group sizes and a single control group, or no concomitant control group, may be artifactual. The most marked effects observed in this study were on the developmental landmarks in the F1 animals induced by exposures after PND 10. Some effects on developmental landmarks and organ weights were observed in F2 animals following exposure either in utero or postweaning. This study therefore does not establish a unique role for exposures in utero or during the early neonatal period.

Abnormalities, Drug-Induced↗
PubMed2002

Normal sexual development of two strains of rat exposed in utero to low doses of bisphenol A.

Pregnant Sprague-Dawley (SD) and Alderley Park (Wistar derived) rats were exposed by gavage during gestation days 6-21 to 20 microg/kg, 100 microg/kg, or 50 mg/kg body weight of BPA with ethinylestradiol (EE; 200 microg/kg) acting as a positive control agent. The sexual development of the derived pups was monitored until termination at postnatal day 90-98. The endpoints evaluated were litter size and weight, anogenital distance at birth, days of vaginal opening, first estrus and prepuce separation, weights of the liver, seminal vesicles, epididimydes, testes, ventral prostate, uterus, vagina, cervix and ovaries, and daily sperm production. Males were terminated at postnatal day 90 and females at postnatal day 98. The only statistically significant effects observed for any dose of BPA were a decrease in daily sperm production and an increase in the age of vaginal opening for the Alderley Park animals at the highest dose evaluated (50 mg/kg). The dose of EE evaluated proved to be maternally toxic in our laboratory, but provided gross evidence of endocrine disruption in the treated dams. These results diverge from those of Chahoud and his colleagues who indicated disturbances to the sexual development of both male and female SD rat pups administered the same 3 doses of BPA. This failure to confirm low dose endocrine effects for BPA is discussed within the context of similar divergent conclusions derived from other assessments of the endocrine toxicity of this agent to rats.

Animals↗
PubMed2001

Replacement of surgical castration by GnRH-inhibition or Leydig cell ablation in the male rat Hershberger antiandrogen assay.

An obstacle to the widespread adoption of the Hershberger antiandrogen assay is the surgical castration procedure required to produce androgen deficiency in the test animals. Here we describe two chemical treatments that produce similar effects to surgical castration. The first is use of ethane dimethane sulphonate (EDS), a specific toxin to the testosterone-producing Leydig cells of the mature testes. The second class of compound is the decapeptide inhibitors of the gonadotrophin-releasing hormone (GnRH), compounds such as Antarelix and Antide. Administration of either EDS or the GnRH inhibitors results in loss of weight of the testes, epididymides, and sex-associated tissues. Co-administration of testosterone to these animals leads to reversal of the induced effects. The basic test protocol for both of these assay modifications is described. Flutamide was used as a representative potent antiandrogen, and DDE as an example of a weakly active antiandrogen. The 5alpha-reductase inhibitor finasteride was used to inhibit the transformation of testosterone to dihydrotestosterone. It is shown that the EDS assay is sensitive to the antiandrogen flutamide, but that it fails to detect the weaker antiandrogen DDE. In contrast, the Antarelix assay performs as well as does the classical castration assay, leading to the detection as antiandrogens of flutamide, DDE, and finasteride. It is concluded that the GnRH inhibition Hershberger assay is more convenient to conduct than the original surgical castration assay, and it involves less stress to the test animals.

5-alpha Reductase Inhibitors↗
PubMed2001

Lack of binding to isolated estrogen or androgen receptors, and inactivity in the immature rat uterotrophic assay, of the ultraviolet sunscreen filters Tinosorb M-active and Tinosorb S.

The presence of structurally diverse chemicals as contaminants in the environment has led to concerns regarding their possible endocrine disturbing effects. Recently, some ultraviolet absorbing components of sunscreen preparations have given positive responses in assays monitoring estrogen-like activity both in vitro and in vivo. Consequently, two recently developed sunscreen components, Tinosorb M-active and Tinosorb S, were evaluated using the in vitro estrogen and androgen receptor competitive binding assays. Neither compound gave a positive response in either of the assays, consistent with the large molecular dimensions of each chemical disfavoring binding to the hormone receptors. Both of the chemicals were inactive in immature rat uterotrophic assays conducted using the subcutaneous route of administration. It is concluded that neither of these agents possess intrinsic estrogenic/antiestrogenic or androgenic/antiandrogenic activity. The several positive control chemicals evaluated gave the expected positive responses in the assays used.

Animals↗
PubMed2000

Obstacles to the prediction of estrogenicity from chemical structure: assay-mediated metabolic transformation and the apparent promiscuous nature of the estrogen receptor.

Information on structure-activity relationships (SAR) and pathways of metabolic activation would facilitate the preliminary screening of chemicals for estrogenic potential. Published crystallographic studies of the estrogen receptor (ER) imply an essential role of the two hydroxyl groups on estradiol (17beta-E(2)) for its binding to ER. The influence of these hydroxyl groups on ER binding and estrogenicity was evaluated by the study of 17beta-E(2) with one or both of these hydroxyl groups removed (17beta-desoxyestradiol and 3, 17beta-bisdesoxyestradiol, respectively). 6-Hydroxytetralin (17beta-E(2) with its C- and D-rings removed) and other synthetic estrogens were also studied. The estrogenicity assays comprised a yeast ER-mediated transcription assay, mammalian cell transcription assays incorporating either ER alpha or ER beta, and the immature rat uterotrophic assay. With the exception of 6-hydroxytetralin in the uterotrophic assay, all the chemicals were active in all the assays. Hydroxylation of the two desoxy compounds to estradiol was shown to occur in immature female rats, but metabolism was not implicated in the responses observed in the ER-binding and yeast systems. It is concluded that the 3-hydroxyl and 17beta-hydroxyl groups of 17beta-E(2) are not absolute requirements for estrogenicity. It would therefore be of value to the derivation of SAR for estrogenicity were the crystal structure of the bisdesoxy-E(2)/ER complex to be evaluated.

Animals↗
PubMed2000

Re-evaluation of the first synthetic estrogen, 1-keto-1,2,3, 4-tetrahydrophenanthrene, and bisphenol A, using both the ovariectomised rat model used in 1933 and additional assays.

1-Keto-1,2,3,4-tetrahydrophenanthrene (THP-1) was reported by Cook et al. in 1933 as the first synthetic estrogen. Estrogenic activity was assessed by the induction of vaginal cornification in ovariectomised rats. The corresponding 4-isomer (THP-4) was shown to be inactive. Both chemicals have been re-synthesised and assessed for hormonal activity. Each chemical bound weakly and to the same extent to isolated estrogen receptors, but only at high concentrations. However, they each lacked estrogenic or anti-estrogenic activity when evaluated in vitro using a yeast hER assay, and both failed to induce vaginal cornification or uterotrophic effects in ovariectomised rats. THP-1, and to a lesser extent THP-4, were shown to possess weak androgenic and anti-androgenic activity in vitro when evaluated using an hAR yeast assay. Estrogenic activity for bisphenol A (BPA) was subsequently demonstrated by [Dodds and Lawson, Synthetic, oestrogenic agents without the phenanthrene nucleus, Nature 137, (1936)] using the same ovariectomised rat protocol, and this activity has been confirmed and supplemented by positive uterotrophic effects for BPA in the same bioassays. The present results illustrate the complexity of deriving conclusions regarding the hormonal activities of chemicals. First, some activities observed in isolated hormonal receptor binding assays may not be expressed in functional hormonal assays. This indicates the need for functional hormonal assays in any screening programme. Second, that activities observed for a chemical in one hormonal assay may not be reflected in related hormonal assays. This indicates the need to define assay protocols with some precision when incorporating them into screening batteries. Finally, that some literature reports of hormonal activity for chemicals may not be capable of independent confirmation under apparently identical conditions of test. This illustrates the need to use lists of hormonally active chemicals with care.

Androgen Antagonists↗
PubMed1999

Hepatic gene mutations induced in Big Blue rats by both the potent rat liver azo-carcinogen 6BT and its reported noncarcinogenic analogue 5BT.

The potent rat liver carcinogen 6-p-dimethylaminophenylazobenzthiazole (6BT) and its reported noncarcinogenic analogue 5-p-dimethylaminophenylazobenzthiazole (5BT; evaluated for carcinogenicity under the similar limited bioassay conditions used for 6BT) have been studied in order to seek an explanation for their different carcinogenic activities. Both compounds act as DNA-damaging agents to the rat liver, and both have now been shown to induce lacI (-) gene mutations in the liver of Big Blue(trade mark) transgenic rats. Both compounds were mutagenic following ten daily gavage doses or following administration in diet for 10 days. Neither chemical induced cell proliferation in the liver following repeat gavage administrations. In contrast, dietary administration of 6BT, and to a lesser extent of 5BT, induced hepatic cell proliferation. The carcinogen 6BT, but not the noncarcinogen 5BT, caused proliferation of oval stem cells in the livers by both routes of administration. It is possible that mutations induced in oval cells by 6BT are responsible for its potent carcinogenicity, and that the comparative absence of these cells in 5BT-treated livers may account for the carcinogenic inactivity of 5BT. Equally, the proliferation of the oval cells may reflect changes in liver homeostasis associated with the liver toxicity observed at the dose level of 6BT used (which was, nonetheless, the dose level used in the positive cancer bioassays). It is concluded that the new data presented cannot explain the differing carcinogenic activities of 5BT and 6BT, and that the reported noncarcinogen 5BT may also be carcinogenic when adequately assessed for this activity.

Animals↗
PubMed1998

Relative activities of methyl methanesulphonate (MMS) as a genotoxin, clastogen and gene mutagen to the liver and bone marrow of MutaMouse mice.

The mutagenicity of the rodent carcinogen methyl methanesulphonate (MMS) to the liver and bone marrow of MutaMouse lacZ- transgenic mice was evaluated. A single intraperitoneal (i.p.) dose of 100 mg/kg MMS gave a strong positive response in the liver UDS and bone marrow micronucleus assays conducted 2 hr and 30 hr, respectively, after dosing. A single i.p. administration of 100 mg/kg of MMS, or five daily administrations of 20 mg/kg MMS, failed to increase significantly the lacZ- --> lacZ+ mutation frequency (MF) in either the liver or the bone marrow, albeit some evidence of weak mutagenicity was observed for the liver. The gene mutation analyses were undertaken 14 days after the final chemical exposure. Administration of the liver mitogens dimethylnitrosamine (DMN), or 4-acetylaminofluorene (4AAF), subsequent to multiple (five) exposures of 20 mg/kg MMS, foiled to enhance the mutagenicity of MMS to the liver, thereby eliminating the possibility that MMS produced promutagenic lesions in the liver that were not transformed to mutations because of the absence of MMS-induced cell division. In the latter experiments, DMN gave a strong mutagenic response and 4AAF a weak mutagenic response. Possible reasons for this selective mutagenicity of MMS (DNA damage and micronuclei induction in the absence of gene mutations) are discussed, but no clear outcome emerges. It is concluded that transgenic mutation assays should not be employed for defining genetic toxicity in vivo, but rather should be reserved for mechanistic studies on previously established rodent genotoxins and/or carcinogens.

2-Acetylaminofluorene↗
PubMed1997

Evaluation of the mutagenicity of acetochlor to male rat germ cells.

Male rat dominant lethal (DL) assays conducted on the herbicide acetochlor are described. Single dose studies conducted at the maximum tolerated dose (MTD, < or = 1000 mg/kg) produced no effects on any of the DL assay parameters at any of the ten weekly sampling periods. It is concluded that acetochlor is non-mutagenic to rat germ cells. Due to initial limited knowledge of the MTD of acetochlor it was also evaluated in the DL assay at a dose level of 2000 mg/kg. At this high dose level severe bodyweight loss and some deaths occurred among the treated animals. In addition, reduced implantations and reduced pregnancy rates were observed at the third sampling period (18-25 days post dosing) in the absence of an increase in early post-implantation deaths. These results indicated that the use of supra-MTD doses of acetochlor had reduced the fertility of the treated males leading to the production of a pseudo-DL assay response, as alerted to and defined by Ehling. Although several such pseudo-DL assay responses have been described, none have been explained mechanistically. It was therefore decided to pursue the effects seen in the DL assay when using supra-MTD doses of acetochlor. Ova analysis of female rats mated with male rats exposed to 2000 mg/kg acetochlor revealed unfertilized ova at the critical third sampling time. Normal fertilization of ova was observed at the first and fifth sampling period and, for a dose of 200 mg/kg acetochlor, at the third sampling period. The magnitude and temporal nature of these effects confirmed the induction of a pseudo-DL assay response, and studies were then undertaken to probe its genesis. Rats treated with 2000 mg/kg acetochlor had normal testicular and epididymal pathology and normal sperm numbers and sperm motility at the critical third sampling period. Despite a small reduction in testicular and epididymal glutathione levels 12 h after exposure to 2000 mg/kg acetochlor, testicular LDH and LDH-X enzyme levels were unaffected. Further, no reduction in the level of free sulphydryl groups (-SH) were observed in epididymal caput sperm heads isolated 0.5, 7 or 14 days after treatment of male rats with 2000 mg/kg acetochlor. The only sperm parameter affected by treatment with 2000 mg/kg acetochlor was an increase in epididymal cauda sperm with head abnormalities. The non-specific nature of this effect was considered inadequate to explain fully the high dose fertility effects seen in the DL assays, which therefore remain unexplained. The present data establish that acetochlor is non-mutagenic to rat germ cells. They also confirm the importance of segregating mutagenic and fertility effects in the DL assay, and emphasize the need for appropriate dose-setting studies prior to the conduct of rodent genetic toxicity assays.

Animals↗
PubMed1997

The rodent uterotrophic assay: critical protocol features, studies with nonyl phenols, and comparison with a yeast estrogenicity assay.

The major protocol features of the immature rat uterotrophic assay have been evaluated using a range of reference chemicals. The protocol variables considered include the selection of the test species and route of chemical administration, the age of the test animals, the maintenance diet used, and the specificity of the assay for estrogens. It is concluded that three daily oral administrations of test chemicals to 21- to 22-day-old rats, followed by determination of absolute uterus weights on the fourth day, provide a sensitive and toxicologically relevant in vivo estrogenicity assay. Rats are favored over mice for reasons of toxicological practice, but the choice of test species is probably not a critical protocol variable, as evidenced by the similar sensitivity of rats and mice to the uterotrophic activity of methoxychlor. Vaginal opening is shown to be a useful, but nondefinitive, adjunct to the uterotrophic assay. The ability of test chemicals to reduce or abolish the uterotrophic response of estradiol is suggested to provide a useful extension of the uterotrophic assay for the purpose of detecting antiestrogens. The results of a series of studies on the environmental estrogen nonyl phenol (NP), and its linear isomer n-nonyl phenol, confirm that branching of the aliphatic side chain is important for activity. 17beta-Desoxyestradiol is shown to be of similar activity to estradiol in the uterotrophic assay and is suggested to represent the "parent" estrogen of NP. Benzoylation of NP and 17-desoxyestradiol did not affect their uterotrophic activity, in contrast to the enhancing effect of benzoylation on estradiol. Selected chemicals shown to be active in the immature rat uterotrophic assay were also evaluated in an in vitro yeast human estrogen receptor transactivation assay. Most of the chemicals gave similar qualitative responses to those seen in the uterotrophic assay, and the detection of the estrogen methoxychlor by the yeast assay evidenced a degree of intrinsic metabolic competence. However, the assay had a reduced ability (compared to rodents) to hydrolyze the benzoate ester of estradiol, and the estrogenic benzoate derivative of NP was not active in the yeast assay. These last results indicate that current metabolic deficiencies of in vitro estrogenicity assays will limit the value of negative data for the immediate future. The results described illustrate the intrinsic complexity of evaluating chemicals for estrogenic activities and confirm the need for rigorous attention to experimental design and criteria for assessing estrogenic activity.

Animals↗
PubMed1997

Assessing the risks of adverse endocrine-mediated effects: where to from here?

This article is based on the closing lecture (by J. Ashby) of the meeting held in Research Triangle Park on January 13-14, 1997-"Assessing the Risks of Adverse Endocrine-Mediated Effects." Several summaries of unpublished data from Zeneca CTL are presented to illustrate concerns over the present absence of agreed criteria for the assessment of endocrine toxicity data. Reference is also made to several points raised by others during the course of the meeting. It is concluded that the substantial challenges currently faced can be met only by strict adherence to the basic principles of good scientific practice, preeminent among which are the needs to confirm data and to respond to them in a cool and dispassionate manner. The wealth of expertise and enthusiasm being devoted to the task in hand, by both governmental and industrial interests, suggests that practical means by which to address the topic of the symposium will be forthcoming in the near future. However, moves to accelerate progress unduly-"to conduct science under the gun"-are already evident. Therefore, if external influences demand that short-cuts must be taken toward achievement of the goals set out in the Wingspread Statement (Colborn and Clement, 1992), such compromises should be clearly identified in order not to confuse the underlying progress that is already evident in this new branch of toxicology.

Animals↗
PubMed1997

Failure to confirm estrogenic activity for benzoic acid and clofibrate: implications for lists of endocrine-disrupting agents.

Earlier reports that benzoic acid is uterotrophic to the rat and mouse and that clofibrate is uterotrophic to the rat have not been confirmed. The studies reported here involved the use of a range of test protocols and dose levels, including the protocols/dose levels used by the original investigators. In addition, both chemicals were inactive in a human estrogen receptor (hER alpha) yeast estrogenicity assay. It is concluded that benzoic acid and clofibrate are not estrogenic in the assays used here. This conclusion has implications for the compilation of lists of endocrine-disrupting chemicals.

Animals↗
PubMed1997

Normal sexual development of rats exposed to butyl benzyl phthalate from conception to weaning.

Butyl benzyl phthalate (BBP) has been administered in drinking water (1000 micrograms/liter) to pregnant AP rats during gestation and lactation. The sexual development of the pups was then monitored until their termination at postnatal day 90 (pnd 90). Pups derived from animals exposed to diethylstilbestrol (DES) in drinking water (50 micrograms/liter) acted as a positive control group. Glass drinking bottles were employed following demonstration of absorption of BBP into plastic drinking bottles. Drinking water intake was monitored and the estimated average exposures of the dams was 182.6 micrograms/kg/day BBP and 8.6 micrograms/kg/ day DES. A total of 240 control pups, 204 BBP pups, and 64 DES pups were obtained for study. The sexual development of both genders of pups was monitored. The body weights of the DES pups were significantly reduced at birth, an effect that persisted until pnd 90. The body weights of the BBP pups were marginally increased at birth, but this difference resolved by pnd 90. DES affected the sexual development of the pups for all endopoints monitored-anogenital (AG) distance on pnd 2; average day of vaginal opening and prepuce separation; uterus, testes, and accessory sex gland weight; and cauda epididymis sperm count and homogenization resistant testicular sperm count at pnd 90. BBP failed to affect any of these parameters, with the exception of a 1.1-day advance in the average day of vaginal opening and a small increase in male AG distance on pnd 2. These last two effects are related to the increased weight of the BBP pups. The incidence of FSH-containing cells in the pituitary gland of animals from each group was unaffected at pnd 90. The effects observed for the DES pups are consistent with the results of earlier studies by Sharpe et al. (Environ. Health Perspect. 103, 1136-1143, 1995). However, the absence of an effect of BBP administration on pup testis weight and testicular sperm count at pnd 90 is in contrast to reductions in these measurements reported earlier by Sharpe et al. (Environ. Health Perspect. 103, 1136-1143, 1995) for similarly derived BBP pups.

Animals↗