Biomedical subjects

R S Calandra

Publications and source records attributed to R S Calandra.

At least 37 records · Page 2Linked to original sources

PubMed1996

Prazosin and stress effect on tumoral growth of 7,12-dimethylbenz[A]anthracene-induced rat mammary tumors.

Repeated isolation stress and prazosin effect were evaluated in 7,12-dimetylbenz[A]anthracene (DMBA) mammary tumors. Tumor volume was significantly lower in stressed than in control animals from 10 to 52 days considering day 1 the moment when tumors became palpable and treatment began. Control Prazosin (0.5 mg/kg) rats showed diminished tumor volume after 40 days. Stress Prazosin curve was similar to stress alone. The proportion of progressing tumors in control was significantly higher than in stressed groups, regardless of Prazosin administration. Body weight gain was similar in every group throughout the experiment. Behavioral studies were performed when stress effect was no longer evident. Grooming and the number of fecal boli were similar in all groups, as well as prolactin serum levels, suggesting that habituation took place. No significant differences were observed between groups for estrogen receptors. However, a greater concentration of progesterone receptors was found in Stressed rats, compared to all other groups. We conclude that the decrease of tumor volume provoked by stress could not be reversed by the alpha 1-adrenergic antagonist prazosin. Then, it appears that the main effect of stress is not mediated by the alpha 1-adrenergic receptors. Higher progesterone receptors in stressed rats could explain the differences observed.

9,10-Dimethyl-1,2-benzanthracene↗

PubMed1995

Atypical androgen receptor in the human melanoma cell line IIB-MEL-J.

To evaluate the presence of androgen receptors in the human melanoma cell line IIB-MEL-J, a Scatchard plot analysis was performed. Cells in culture revealed a single binding component with an apparent dissociation constant (KD) at 37 degrees C of 11 nM and a binding capacity of 326 fmol/mg protein when measured with [3H]-R1881. Competition analysis revealed an atypical relaxation of specificity, since not only androgen (testosterone, dihydrotestosterone [DHT], R1881) and antiandrogen (hydroxy-flutamide [OH-FLU]) competed for [3H]-R1881 binding, but also estradiol, progesterone, and cortisol at 500-fold excess concentration. Binding of [3H]-estradiol and [3H]-R5020 in the absence of unlabeled DHT were completely suppressed in its presence. Immunohistochemistry of androgen receptor with a monoclonal antibody showed that nuclei were vigorously stained. Different doses of flutamide (FLU) and OH-FLU tested on cultured IIB-MEL-J cells in the presence of serum inhibited significantly cell proliferation in a dose-dependent manner. When cells were incubated with 10 nM DHT and 1% charcoal-adsorbed serum, a significant stimulation of growth that was observed was inhibited by 4 microM OH-FLU. DHT stimulation was completely reversed by the antiestrogen tamoxifen. In addition, male nude mice transplanted with IIB-MEL-J tumor were treated with FLU when tumors were palpable. FLU was effective in diminishing tumor growth and increasing survival rate of the animals. As a conclusion, the presence of functional androgen receptors in these cells has been demonstrated by growth inhibition in vitro and in vivo with antiandrogens, and their atypical nature is suggested by binding cross-reactivity and competition studies.

Androgen Antagonists↗

PubMed1994

Modulation of ornithine decarboxylase activity by prolactin in seminal vesicles of the rat.

The stimulatory effect of prolactin on sexual accessory glands is well established, though the mechanism of trophic action remains poorly understood. We have therefore assessed the effect of high levels of prolactin on ornithine decarboxylase activity and polyamine content in seminal vesicles (SV) of adult rats. Hyperprolactinaemia was induced by implantation of tissue fragments of a prolactin-secreting tumour 7315a, and the rats killed at 35 days post-inoculation. Serum levels of prolactin were increased significantly (p < 0.001) in tumour-bearing rats. Levels of testosterone in serum were reduced markedly, whereas LH levels remained unchanged. SV weight in the experimental group was not significantly different from that in the corresponding control group. A clear increase in ornithine decarboxylase activity of SV was observed (p < 0.001) in the hyperprolactinaemic rats. However, there was no change in the polyamine content of SV in tumour-bearing rats, compared to the control group. These results indicate that ornithine decarboxylase activity in SV of adult rats is regulated mainly by prolactin. This experimental model may be useful for identification of some of the events involved in the trophic action of prolactin.

Animals↗

PubMed1993

Effect of bilateral denervation of the immature rat testis on testicular gonadotropin receptors and in vitro androgen production.

We have studied the effect of superior spermatic nerve (SSN) section on testicular gonadotropin receptors and in vitro androgen production by immature rat testis. Bilateral testicular denervation had no effect on testicular weight, serum androgens, LH, FSH and PRL levels. Denervation resulted in a significant inhibition of hCG stimulated in vitro androgen production. A reduction in the number of testicular LH receptors was observed after SSN section, while FSH binding sites remained unchanged. These results indicate that the number of LH receptors and testicular steroidogenic response to hCG are influenced by nerves reaching the testis.

Androgens↗

PubMed1992

Somatotropic and lactotropic receptors in transgenic mice expressing human or bovine growth hormone genes.

The somatotropic and lactotropic receptors were studied in liver microsomal preparations from transgenic mice carrying the human growth hormone (hGH) or bovine growth hormone (bGH) gene fused to mouse metallothionein-I (MT) or phosphoenolpyruvate carboxykinase promoter/regulator (PEPCK). Specificity studies indicated that, similarly to normal mice, liver microsomes from the transgenic animals possess a mixed population of somatotropic and lactotropic binding sites. In transgenic animals of both sexes, the binding capacity of somatotropic receptors was significantly increased without corresponding changes in affinity. Expression of the MT-hGH hybrid gene was associated with the induction of somatotropic receptors which was approximately twice as great as that measured in animals expressing the MT-bGH hybrid gene. The binding capacity of lactotropic receptors in liver microsomes (quantitated by the use of labelled ovine prolactin) was increased 2-3 fold in transgenic females and approximately 10-fold in transgenic males as compared to the respective normal controls. We conclude that lifelong excess of GH up-regulates hepatic GH and prolactin receptors, and that lactogenic activity of GH is not essential for induction of prolactin receptors in the liver of transgenic mice.

Animals↗

PubMed1992

Identification of somatogenic binding sites in liver microsomes from normal mice and transgenic mice expressing human growth hormone gene.

Somatogenic binding sites were detected and characterized in microsomal preparations from livers of normal mice and mice expressing metallothionein-I/hGH (mMT/hGH) hybrid gene, using 125I-labelled bovine or human GH, or a photoreactive derivative of hGH (125I-AP-hGH1). Specific binding of 125I-bGH was detected in liver microsomes from both normal and transgenic mice with an apparent Kd of 2 nM. 125I-hGH was partially displaced by bGH. 125I-AP-hGH1 was covalently bound to the microsomal preparations, and bGH prevented the formation of the 130 kDa species with no appreciable effect on 63 kDa and 70 kDa lactogenic complexes.

Animals↗

PubMed1992

Down regulation of masked and unmasked insulin receptors in the liver of transgenic mice expressing bovine growth hormone gene.

The interaction of insulin with its receptor was studied in microsomes from livers of transgenic mice expressing the bovine growth hormone gene with mouse metallothionein-1 promoter (MT/bGH) and in their normal (non-transgenic) littermates. Specific binding of 125I-insulin was detected in hepatic microsomes from normal and transgenic mice with an apparent Kd of 8 and 200 nM, for high and low affinity sites, respectively. The transgenic MT/bGH mice had a marked hyperinsulinism without significant elevation of plasma glucose levels. Under identical conditions of preparation and incubation, microsomes from the transgenic male and female mice bound 39% and 34% less insulin than those from their litter mates. Scatchard's analysis indicates that this decrease in binding is due to a decrease in the number of receptor sites. In contrast to the marked decrease in insulin binding to unmasked receptors, the levels of masked (also called cryptic) insulin receptors were similar (or slightly increased) in transgenic mice microsomes as compared to those of their normal litter mates.

Animals↗

PubMed1992

Androgenic control of polyamine concentrations in rat epididymis.

Unilateral orchidectomy resulted in a significant decrease in tissue content of putrescine and polyamines. However, no differences were detected when the results were expressed in terms of ng g-1 tissue. At 48 h after bilateral orchidectomy, a significant decrease in putrescine content was observed, but spermidine and spermine content were unaffected. The observed decrease in putrescine was prevented by treatment with testosterone propionate, but neither spermidine nor spermine were affected. Bilateral orchidectomy resulted in a significant decrease in the tissue content of putrescine, spermidine and spermine after 7 days. Treatment with testosterone propionate increased the content of putrescine, spermidine and spermine in the epididymis by about 200%, 92% and 34%, respectively. When results were expressed as nmol g-1, a significant decrease after castration in putrescine and spermidine, but not in spermine, was observed. Treatment with testosterone propionate restored putrescine concentration, but had no effect on spermidine and spermine concentrations. In castrated rats treated with testosterone propionate, the anti-androgen flutamide abolished the effect of the androgen on putrescine and spermidine content, but there was no effect on spermine. Acetylputrescine was not detected in the epididymis, while acetylpolyamines were detected at much lower concentrations than polyamines. After bilateral orchidectomy there was a decrease in the tissue content of all acetylpolyamines and an increase in their tissue concentration. The effect of castration on acetylpolyamine content was reversed by testosterone propionate treatment. We conclude that an active synthesis of polyamines occurs in the rat epididymis, and that this process depends upon the androgen environment. Regulation of ornithine decarboxylase activity appears to be the main step that is controlled by androgens.

Androgens↗

PubMed1991

Effect of long term diazepam administration on testicular benzodiazepine receptors and steroidogenesis.

We evaluated the effect of acute and chronic diazepam administration on testicular peripheral type benzodiazepine receptors (PBZD-R), serum testosterone and LH levels and the "in vitro" androgen production in response to Ro 5-4864, a PBZD-R agonist. The chronic diazepam treatment induced a significant fall in plasma testosterone concentration while LH levels remained unchanged. The number of PBZD-R was reduced by 37% and low concentrations (10(-8)-10(-6) M) of Ro 5-4864 failed to stimulate "in vitro" androgen production. The acute diazepam administration caused a significant increase in plasma testosterone levels while no changes were observed in LH concentrations and testicular PBZD-R. These results further suggest a modulatory role of PBZD-R on testicular steroidogenic activity.

Androgens↗

PubMed1991

Cyclic adenosine monophosphate (cAMP) does not mediate the stimulatory action of norepinephrine on testosterone production by the testis of the golden hamster.

The role of cAMP in mediating the stimulatory effects of norepinephrine (NE) on testosterone (T) production by hamster testes in vitro was examined using tissue from both gonadally active and gonadally regressed hamsters. As expected from our previous studies, the NE-induced increase in T accumulation in this system was prevented by alpha-adrenoreceptor antagonist prazosin, but not by beta-adrenoreceptor antagonist propranolol. In incubations of regressed testes from short photoperiod-exposed hamsters, NE stimulated accumulation of cAMP in media and tissue. These effects were prevented by propranolol but not by prazosin. In incubations of active testes from long photoperiod-exposed animals, NE stimulated cAMP in the media but not in the tissue, and potentiated the effect of hCG on the accumulation of cAMP only in tissue. When added to incubations with NE and hCG, propranolol, but not prazosin, reduced cAMP levels in media and tissue. Thus, functional alpha- and beta-adrenoreceptors are present in active and regressed testes and can be activated by NE. NE stimulates cAMP production via its action at the beta-receptors and T production via its action at the alpha-receptors. These results imply that cAMP does not mediate the stimulatory action of NE on T production in hamster testes.

Animals↗

PubMed1991

Effects of hyperprolactinemia on ornithine decarboxylase activity and polyamine levels in seminal vesicles of genetically prolactin-deficient adult dwarf mice.

Prolactin (PRL) has been shown to exert many different actions in various biological systems. Polyamines are known to influence the growth and function of the seminal vesicles (SV). Furthermore, ornithine decarboxylase (ODC) is considered a key enzyme in the biosynthesis of polyamines and is regulated by PRL in certain target tissues. Adult Ames dwarf mice (df/df), genetically deficient in PRL, were used for this study. The experimental groups were as follows: Group 1, pituitary-grafted; Group 2, sham-operated; Group 3, castrated + testosterone propionate (TP)-treated (25 micrograms/mouse, 3 times/wk, s.c.) + grafted; and Group 4, castrated + TP as above. The animals were killed 40 days later, and polyamines and ODC activity in SV and liver were determined. Serum PRL, FSH, and testosterone (T) were also measured. In the grafted groups, there were significant elevations in serum PRL and FSH levels. In the gonad-intact, pituitary-grafted group, animals exhibited an elevation in plasma T levels, and similar levels were achieved in the castrated, androgen-replaced groups. In hyperprolactinemic mice, the weights of SV were significantly greater than in the corresponding control groups. The relative weights of the SV showed a similar pattern. An increase in ODC activity was observed in both SV and liver in hyperprolactinemic groups. In those animals in which serum T levels were held constant, an increase in the enzyme activity in SV was detected in hyperprolactinemic group whereas in liver, no significant difference was observed. Concentrations of polyamines in the SV were increased in hyperprolactinemic, castrated, TP-treated mice. The present results indicate that PRL can exert a direct stimulatory effect on the growth, ODC activity, and polyamine levels in the SV.

Animals↗

PubMed1991

Coexistence of gamma-aminobutyric acid type A and type B receptors in testicular interstitial cells.

The existence of specific gamma-aminobutyric acid (GABA)ergic receptors in testicular interstitial cells was investigated in the present study. Specific binding of [3H]GABA to interstitial cell membranes was found to be time- and temperature-dependent and varied according to Ca2+ concentration present in the incubation medium. We analyzed the ability of different GABAergic agonists and antagonists to displace the bound radioactivity. In the absence of Ca2+ (1 mM EDTA), GABA and the GABAergic agonist isoguvacine displaced the bound radioactivity. When the radioligand assay was performed in the presence of 2.5 mM CaCl2, the [3H]GABA specifically bound increased twofold. Under such conditions, the specific GABAergic agonist baclofen, as well as GABA and isoguvacine, displaced the [3H]GABA bound. Saturation analysis revealed the presence of a population of GABAA binding sites with a KD value of 45.2 nM and a maximal number of binding sites of 57.4 fmol/mg of protein. The maximal binding increased on addition of 2.5 mM CaCl2 to 102 fmol/mg of protein, indicating the existence of a second population of GABAergic receptors, i.e., type B, with essentially the same affinity. In addition, the incubation of testicular interstitial cells with GABA and baclofen resulted in an increase in androgen production. These results support a functional role of GABA in the neuroendocrine control of the male gonad.

Ammonium Chloride↗

PubMed1990

Peripheral-type benzodiazepine receptors are highly concentrated in mitochondrial membranes of rat testicular interstitial cells.

The binding of 3H-RO 5-4864 to the peripheral-type benzodiazepine receptors (PBZDR) in rat testicular interstitial cells (TIC) was characterized. The binding was saturable, reversible and showed a single high-affinity (Kd = 5.02 +/- 0.86 nM) class of binding sites. The maximal binding capacity (Bmax) in crude mitochondrial fractions (77.6 +/- 9.1 pmol/mg protein) represents the highest density of PBZDR in tissues thus far studied. In comparison with the crude mitochondrial fraction the subcellular fractionation of TIC revealed a 2-fold enrichment of 3H-RO 5-4864 binding sites to the purified mitochondria (Bmax = 140 +/- 23 pmol/mg protein). The ability of various drugs to displace 3H-RO 5-4864 from TIC binding sites was examined and the inhibition constants (Ki) for RO 5-4864, PK 11195, diazepam and flunitrazepam were 3.5, 4.4, 159, and 353 nM, respectively, whereas clonazepam and RO 15-1788 were inefficient in displacing 3H-RO 5-4864 (Ki greater than 10 microM). This pharmacological profile is characteristic of PBZDR described in other tissues. In conclusion, rat TIC possess a very high concentration of PBZDR primarily associated with mitochondrial membranes.

Animals↗

PubMed1990

Serotonergic innervation of the rat testis.

The presence of 5-hydroxytryptamine (5-HT) was determined by h.p.l.c. in perchloric extracts of each isolated compartment of the adult rat testis. The testicular capsule, interstitial cells and interstitial fluid contained 5-HT, but 5-HT was not detected in the tubular compartment. In a group of adult rats, one testis was unilaterally denervated, and the contralateral testis used as control. The superior spermatic nerve, arising from the renal plexus, was excised and 1 week after surgery 5-HT content was measured in the capsule and interstitial fluid of both testes. Denervation caused a significant fall (34%) in 5-HT content. These results indicate that at least part of the testicular 5-HT derives from a serotonergic innervation of the gonad.

Animals↗

PubMed1989

Cytoplasmic steroid receptors in tumoral and "normal" endometrial samples from symmetrical uterine zones.

Cytosol progesterone (PgR) and estradiol (E2R) receptors were quantified simultaneously in "normal" and tumoral endometrium samples, located symmetrically on the longitudinal axis of the uterine cavity. With this experimental model two different groups of patients were detected. In the first group (7 of 10 women), the endometrial carcinoma had a greater cytosolic concentration of PgR than the corresponding "normal" endometrium, both kinds of tissue being affected by the same circulating hormonal "environment," peculiar to each patient. The opposite occurs in the other group (3 of 10 women), since the "normal" endometrium was found to be "richer" in receptors than the tumoral endometrium. It is suggested that this difference in the capacity of the tumor for synthesizing PgR and even E2R as compared to the "normal" endometrium may be a marker which improves selection of patients who will be more likely to respond favorably to endocrine therapy.

Aged↗

PubMed1989

Testicular interstitial cells as targets for peripheral benzodiazepines.

We evaluated the 'in vitro' effect of a selective peripheral benzodiazepine (BZD) receptor agonist, Ro 5-4864, on basal and hCG-stimulated androgen production by testicular interstitial cell suspensions. Ro 5-4864 (10(-9)-10(-5) M) induced a significant increment of basal testosterone release into the medium. In addition, under conditions of hCG stimulation, Ro 5-4864 (10(-7) M) induced a potentiated response to the gonadotropin in a dose-dependent manner. The selective peripheral BZD antagonist PK 11195 fully prevented the stimulatory effect of Ro 5-4864. On the other hand, clonazepam, a central BZD agonist, failed to affect androgen production significantly, whereas diazepam (10(-5)-10(-4) M), which binds to both central and peripheral BZD receptors, was able to induce a significant increment of basal and hCG-stimulated testosterone production. These results suggest that under our experimental conditions Ro 5-4864 exerts an effect on testicular steroidogenesis, presumably through binding to the previously described peripheral-type BZD receptor.

Animals↗

PubMed1989

Effect of the antiandrogen flutamide on pituitary LH content and release.

Flutamide is a nonsteroidal antiandrogen that blocks androgen receptors, with a consequent increase in serum immunoreactive LH (I-LH) in the presence of high testosterone concentrations. Several studies suggested that the gonadal steroids also play an important role in the regulation of LH bioactivity (B-LH). Therefore, it seems difficult to understand how the blockade of pituitary androgen receptors leads to the increase in testosterone levels. The present study was designed to elucidate the effect of flutamide on serum I-LH, B-LH and testosterone, as well as on in vitro stimulation of pituitaries by gonadotropin-releasing hormone (GnRH), in intact and androgen-treated castrated rats. In intact animals, a dose of flutamide as low as 0.5 mg/day provoked a 7- to 8-fold increase in serum I-LH levels over the vehicle-injected controls, whereas B-LH and testosterone were unaffected. However, higher doses significantly increased serum B-LH to values similar to those obtained in vehicle-injected castrated animals, resulting in high testosterone levels. Flutamide treatment provoked a decrease in I-LH and B-LH pituitary content; this effect was significantly higher under in vitro GnRH stimulation. The releasable I-LH under GnRH stimulation was not affected by flutamide treatment; however, a marked decrease was observed in B-LH.(ABSTRACT TRUNCATED AT 250 WORDS)

Anilides↗

PubMed1988

Ornithine decarboxylase activity as a marker of androgen and antiandrogen action in the rat epididymis.

After castration, there was a marked decrease in serum androgen concentration at 6 h, and a dramatic inhibition of ornithine decarboxylase (ODC) at 12 h. Administration of testosterone propionate to castrated rats at a dose of 0.05 mg/animal restored ODC activity to the normal value. However, no change was observed when intact rats were treated with testosterone even at a 40-fold higher dose, indicating that endogenous androgens present in intact rats are far in excess for maintenance of maximal levels of activity. Administration of the antiandrogen flutamide to intact rats caused a moderate decrease in epididymal weight, whereas this effect was more pronounced in castrated, androgen-treated rats. In the latter, the effect of flutamide was significant at the lowest dose used (0.5 mg/day). ODC activity was significantly decreased by flutamide treatment of intact rats, but even at the highest dose used (10 mg/day) only a 39% inhibition was observed. In flutamide-treated rats, LH concentrations were markedly increased, as were serum and epididymal androgens. In androgen-treated castrated rats, flutamide caused epididymal ODC to fall to undetectable values. These results show that: (1) androgens are essential for the maintenance of ODC activity in the epididymis; (2) epididymal ODC activity is maximally stimulated by endogenous androgens, at least in the pubertal rat; (3) the apparent potency of flutamide is substantially lowered by an increase in epididymal androgens. We suggest that ODC is a sensitive marker of the action of androgens and antiandrogens in the epididymis.

Androgens↗