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G W Lucier

Publications and source records attributed to G W Lucier.

At least 127 records · Page 7Linked to original sources
PubMed1984

Cytosolic and nuclear estrogen receptors in the isolated perfused rat liver.

The isolated perfused rat liver was investigated as a potential model to analyze binding of 17 beta-[3H]estradiol (E2) to cytosolic and nuclear estrogen receptors. Viability of the isolated perfused liver was monitored by measuring leakage of cytosolic enzymes into the perfusate. These studies indicated that the liver remained viable for at least a 90-min perfusion period although significant decreases in cytosolic estrogen receptor concentrations occurred during this perfusion period. Estrogen receptor loss was minimized by supplementing the red blood cell-free perfusion medium with 5 micrograms of insulin per ml. Uptake of [3H]E2 by hepatic cytosolic estrogen receptors of the isolated perfused liver was rapid as measured by partial purification of radiolabeled ligand receptor complexes after varying times of perfusion. Peak liver concentrations of receptor-bound E2 were achieved 15 min after the onset of perfusion when using livers from either male or female rats. After 15 min, radiolabeled cytosolic ligand receptor complexes decreased rapidly, reaching lowest concentrations at 60 min. Radiolabeled salt-extractable nuclear-binding sites increased up to 30 min and then decreased slightly between 30 and 90 min. Both 4S and 5S forms of nuclear binding sites were detected in the isolated perfused livers as evaluated by sedimentation analysis on 5 to 20% sucrose density gradients. Concentrations of radiolabeled cytosolic and nuclear receptors were greater in females than males at all perfusion periods examined when the initial concentration of [3H]E2 was 4 nm. Sex differences in receptor uptake were not as great when higher concentrations of [3H]E2 were added to the perfusion medium. These studies suggest that the isolated perfused liver is a suitable model to investigate short-term uptake of estrogens by cytosolic and nuclear receptors.

Animals↗
PubMed1983

Imprinting of hepatic estrogen-binding proteins by neonatal androgens.

Previous studies discovered a second class of estrogen-binding proteins distinct from estrogen receptor which exhibited higher capacity, lower affinity (HCLA) binding properties. HCLA sites underwent postpubertal sex differentiation, such that adult male levels were at least 10-fold higher than adult female levels. Neonatal castration of male rats prevented the subsequent sex differentiation of HCLA binding sites; adult male rats that were castrated neonatally exhibited typically female concentrations of these binding sites. If male rats were castrated at 19 days of age or later, postpubertal sex differentiation of HCLA binding sites proceeded as observed for intact males. Administration of testosterone propionate (TP) to castrated (neonatally) males during a critical period (days 6-13) imprinted for the subsequent sex differentiation of HCLA sites, whereas TP administration at other times did not. The expression of these imprinted sites was not manifested until puberty, as neonatal manipulation or TP treatment had no effect on HCLA sites in immature rats. The imprinted effect on HCLA binding sites appeared to be permanent and irreversible. Treatment of castrate males with diethylstilbestrol (DES) or zearalenol (P-1496) during the critical period was incapable of restoring development of normal male levels of HCLA sites. Competitive binding studies using several steroid hormones revealed similar data for intact males and castrate (neonatal) male rats that had received TP during the critical period. These studies demonstrate an early imprinting period during which androgen exposure programs for postpubertal development of sex differentiation of HCLA binding sites.

Animals↗
PubMed1983

Influences of sex steroids on experimental carcinogenesis.

Sex steroids can apparently modify hepatic function in at least two ways (Figure 1). First, the liver contains specific receptor proteins for either androgens or oestrogens. Several studies, using effects on the monooxygenase system as an indicator of hormone action, have shown good correlations between the presence of sex-steroid receptors and hepatic response to these hormones. In general, androgens induce the activities of drug biotransformation reactions, whereas oestrogens depress them. Second, the endocrine milieu, during a critical period of early development, apparently programmes the hypothalamic-pituitary axis to release factors which cause certain aspects of liver biochemistry to undergo sex differentiation. Selected components of the cytochrome P-450 system exhibit sex differences, and these differences are imprinted by neonatal androgens and are initiated and maintained by the pituitary gland. Corresponding to sex differentiation of the hepatic monooxygenase system are significant sex differences in responses to hepatocarcinogens such as N-2-fluorenylacetamide and N-hydroxy-N-2-fluorenylacetamide. Higher incidences of hepatocellular carcinomas in males appear to result from exposure to neonatal androgens.

Androgens↗
PubMed1983

Hepatic estrogen responsiveness. Possible mechanisms for sexual dimorphism.

In addition to estrogen receptors, liver contains a second class of estrogen-binding proteins referred to as higher-capacity, lower-affinity (HCLA) binding sites which are distinct from estrogen receptors. HCLA sites comprise two classes of proteins: moderate-affinity (KD = 0.45 microM and 0.24 microM) estrogen-binding sites unique to male cytosol and a low-affinity, nonsaturable estrogen-binding site present in both sexes. The sex differences observed in HCLA sites are apparently a consequence of imprinting by testicular androgen during a critical neonatal period. Neonatal castration causes a reduction in the concentration of HCLA sites in the subsequent adult male. Furthermore, the moderate-affinity sites detected by Scatchard analysis in adult male liver are not observed in neonatal castrates. Cell-free nuclear translocation assays demonstrate that nuclear uptake of cytosolic receptor-ligand complexes is more efficient in females than in males. This sex difference in nuclear uptake can be minimized when the concentration of the ligand is increased to a level necessary to saturate the estrogen receptor in the presence of HCLA sites. Nuclear uptake of receptor-ligand complexes in neonatally castrated males (deficient in HCLA sites) is similar to that seen in adult females. Elevations of serum triglyceride following estradiol exposure have been monitored as an indicator of hepatic responses to estrogen. Our studies have shown that female liver appears more responsive to estrogen exposure than does male liver. While a dose of 20-30 micrograms of estradiol per kilogram of body weight per day was sufficient to produce a 3- to 4-fold increase in the concentration of triglyceride associated with the very low-density lipoprotein fraction in females, a dose of 100 micrograms of estradiol per kilogram of body weight per day was needed to obtain a similar response in males. However, following neonatal castration, estrogen responsiveness in the subsequent adult male rat was similar to that in females, suggesting a role for neonatal androgens in regulating sex differences in the action of hepatic estrogen.

Animals↗
PubMed1982

Altered imprinting of rat liver monoamine oxidase by o, p'-DDT and methoxychlor.

Neonatal administration of o,p'-DDT [1, 1, 1-trichloro-2-(o-chlorophenyl-2-(chlorophenyl)ethane] or methoxychlor resulted in elevated levels of sex-differentiated hepatic monoamine oxidase activities in adult rats, but not in prepubertal animals. Exposure to these hormonally active xenobiotics may have changed the brain hormone environment during the critical period of development, resulting in endocrine alterations that were reflected by latent but permanent increases in hepatic monoamine oxidase activities, i.e. "altered imprinting". Hepatic glutathione S-transferases and cytochrome P-450 content also underwent sex differentiation, but neonatal treatment with o,p'-DDT or methoxychlor did not alter levels in adult rats. However, glutathione S-transferase activities and cytochrome P-450 content were higher in prepubertal animals treated neonatally with o,p'-DDT. In contrast to monoamine oxidase, effects on glutathione S-transferase activities and cytochrome P-450 content were attributed to induction by these xenobiotics.

Animals↗
PubMed1982

Effects of polychlorinated biphenyls on the development of intestinal and serum marker enzymes.

The effects of polychlorinated biphenyls (PCBs) on the development of several intestinal and serum marker enzymes have been studied. The three congeners 4-monochloro (1-CB), 3, 4, 3',4'-tetrachloro (4-CB), and 2, 4, 5, 2', 4, 5'-hexachloro (6-CB) biphenyl were administered orally to pregnant rats on d 8, 11, 13, 15, and 18 or gestation. 1-CB and 6-CB were intubated at doses of 30 mg/kg.d (total dose, 150, mg/kg) and 4-CB was administered at 3 mg/kg-d (total dose, 15 mg/kg). Levels of intestinal alkaline phosphatase, monoamine oxidase, and Na+, K+-adenosin-5'-etriphosphatase and levels of serum alkaline phosphatase, sorbitol dehydrogenase, and beta-hydroxybutyrate dehydrogenase were measured in the dams after weaning and in their offspring at -1, 6, 20, and 55 d of age. Intestinal alkaline phosphatase activity was elevated at the later postnatal stages in the 1-CB group and depressed at 55 d in the 4-CB group, whereas serum alkaline phosphatase levels were markedly depressed prenatally and postnatally in the 4-CB and 6-CB groups, respectively, Intestinal monoamine oxidase levels were markedly increased in the 6-CB group at -1, 6, and 20 d of age and significantly depressed in the 4-CB animals at -1 and 55 d of age. There was an increase in monoamine oxidase activity in the 4-CB group at 6 d. The 1-CB group exhibited depression of monoamine oxidase levels at 6 and elevation at 20 and 55 d. Intestinal Na+, K+-ATPase levels were elevated throughout development in the 1-CB animals and at -1 and 6 d in the 4-CB group. The 6-CB animals showed elevated levels of Na+, K+-ATPase only at 6 d. Serum beta-hydroxybutyrate dehydrogenase and sorbitol dehydrogenase were induced prenatally in the 4-CB animals but enzyme activities decreased to normal by 55 d of age. Significant depression of activity was evident in the 1-CB and 6-CB groups at -1 d in both enzymes. Dams in the 1-CB group showed significant changes in intestinal monoamine oxidase, serum sorbitol dehydrogenase, and serum alkaline phosphatase. Serum levels were elevated in the 4-CB group. Activities of intestinal enzymes remained unchanged in the 4-CB group. All maternal enzyme levels monitored were not significantly changed in the 6-CB group.

Alkaline Phosphatase↗
PubMed1981

Sex differences in hepatic oestrogen-binding proteins.

Gel-filtration (Sephadex G-75) analysis of hepatic cytosol reveals both qualitative and quantitative sex differences in oestrogen-binding proteins. The elution profile of [(3)H]oestradiol-labelled cytosol shows four species of oestrogen-binding proteins (peaks I, II, IV and V) common to both sexes. The amount of [(3)H]oestradiol binding in peak I is equivalent in both males and females and corresponds quantitatively to the specific oestrogen receptor. The amount of binding in the remaining three peaks is greater in males than females. In addition, an oestrogen-binding protein (peak III) is present that is unique to male cytosol. Proteinase-inhibition studies demonstrate that the observed multiplicity of oestrogen-binding proteins is not an artefact of proteolytic breakdown. Sex differences in oestrogen-binding proteins are absent in immature male and female animals; the oestrogen-binding protein profile in immature rats resembles that of an adult female. Gonadectomy of adult animals does not affect the oestrogen-binding-protein profile. In contrast, neonatal (day 1) castration results in partial feminization of the characteristic oestrogen-binding protein profile seen in the adult male; the appearance of Peak III is suppressed and marked decreases in the amount of oestradiol binding occurs in the remaining peaks. Hypophysectomy of adult animals results in near abolishment of the observed sex differences; the male oestrogen-binding protein profile is partially feminized and the female profile is partially masculinized, as characterized by the appearance of [(3)H]oestradiol binding in the region of peak III and increased amounts of binding in peaks IV and V. The present studies demonstrate a multiplicity of oestrogen-binding proteins in liver cytosol and raise the possibility that the presence of some of these proteins may be imprinted at birth through the hypothalamic-pituitary axis, by a mechanism requiring neonatal androgen exposure.

Animals↗
PubMed1981

Effect of gonadectomy on the ontogeny of estrogen-binding components in rat liver cytosol.

These studies elucidate the ontogeny of two classes of estrogen-binding sites present in rat liver cytosol. The first class of sites is precipitated from whole cytosol fractions by ammonium sulfate (30% saturation) and exhibits characteristics of specific estrogen receptors. Detectable levels of receptors are attained during the third postnatal week. During days 30--40, receptors reach maximum concentration and remain relatively constant thereafter. The second class of sites, detected in whole cytosol fractions, possess a high binding capacity for estrogens and are present in similar amounts in male and female liver before day 34. However, between days 34--40 male levels increase dramatically while female levels remain constant. This sex difference is maintained throughout the duration of the study (160 days). Specific estrogen receptors from immature (26 days) and mature (70--80 days) rat liver have similar characteristics in terms of sedimentation properties in sucrose gradients, ligand binding specificity, and heat and pronase susceptibility. After prepuberal (19--21 days) gonadectomy, levels of receptor in subsequent adult animals of both sexes are increased approximately 40%. No alterations in receptor levels are seen after neonatal (day 1) castration of males. Prepuberal (day 19) gonadectomy does not alter the normal development of sexual differentiation of high capacity estrogen-binding sites. However, after neonatal (day 1) castration male rats, levels of those sites do not undergo sexual differentiation, and neonatally castrated adult males exhibit female levels of high capacity estrogen-binding site. These studies suggest that sexual differentiation of high capacity estrogen-binding sites may be programmed at birth by testicular androgens.

Aging↗
PubMed1981

Altered sex differentiation of hepatic ethylmorphine N-demethylation in the male rat following neonatal methadone exposure.

Since acute methadone treatment reduces serum androgen levels in adult male rats, we have investigated the effect of exposure of neonatal rats to methadone (M) on the "neonatal imprinting" of hepatic monooxygenase by testosterone. The kinetic constants for ethylmorphine N-demethylation (ED) in hepatic microsomes of adult rats are sex-related (female Km greater than male Km and male Vmax greater than female Vmax). Treatment of male neonates with M (2.5 mg/kg, sc) during the first 5 postnatal days resulted in an elevation of the Km, but no significant changes in the Vmax for ED in adult life. The M-induced "feminization" of the Km for ED could be prevented by a single dose of testosterone propionate (TP) given to the neonates on day 2 following birth. M treatment also reduced in a reversible manner neonatal serum androgen levels: Decreased androgen levels were not observed beyond the fifth postnatal day. These data suggest that the feminizing effect of M may be related to a reversible chemical castration effect during a critical neonatal period. Our studies also show that the imprinting of the Km and Vmax for ED do not occur during the identical period.

Animals↗