Altered Androgen Receptor Research Articles

Abstract 4556: AR intragenic rearrangement and altered androgen receptor mRNA splicing in castration-resistant prostate cancer

Abstract Androgen depletion for advanced prostate cancer (PCa) targets activity of the androgen receptor (AR), a steroid receptor transcription factor required for PCa growth. The emergence of lethal castration-resistant PCa (CRPCa) is marked by aberrant re-activation of the AR despite ongoing androgen depletion. Recently, alternative splicing has been described as a mechanism giving rise to COOH-terminally truncated, constitutively active AR isoforms that can support the CRPCa phenotype. However, the pathologic origin of these truncated AR isoforms has not been described. The goal of this study was to investigate alterations in AR expression arising in a cell-based model of PCa progression driven by truncated AR isoform activity. We demonstrate that stable, high-level expression of truncated AR isoforms in 22Rv1 CRPCa cells coincides with intragenic rearrangement of a ∼35kb AR genomic segment, which contains several alternative AR exons. Analysis of metastatic CRPCa tissues indicated that related AR copy number alterations are frequent and often occur in conjunction with high-level AR amplification. Nucleotide-level resolution of the break fusion junction in 22Rv1 cells revealed a DNA repair signature consistent with a microhomology-mediated, replication-based mechanism of origin. Together, these data provide the first report of AR intragenic rearrangements in CRPCa and a link with pathologic expression of truncated AR isoforms in a cell-based model of PCa progression. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4556. doi:10.1158/1538-7445.AM2011-4556

Abstract 1937: Nemo-like kinase expression is altered during prostate cancer progression

Abstract MAPKs have been implicated in cancer progression. We have previously shown that Nemo-like kinase (NLK) inhibits androgen receptor signaling and induces apoptosis in prostate cancer cell in vitro. The objective of this study was to investigate NLK expression in clinical samples of primary prostate cancer and in prostate cancer xenografts using immunohistochemistry. TMAs containing primary prostate cancer samples and prostate cancer xenograft tissues were used. Our data show that NLK immunoreactivity is 0.34 higher in primary prostate cancer vs. normal prostate epithelium (p=0.01) but our analysis did not reveal any significant correlations of NLK immunoreactivity with PSA, Gleason score or recurrence of the disease. When we examined NLK immunoreactivity in prostate cancer xenografts our results show that there are signficant differences in cellular localization of NLK between xenografts that respond well to castration vs. those that do not. Xenografts that respond well to castration exhibit lower levels of NLK in nucleoplasm and higher leves of NLK in nucleoli vs. xenografts that do not respons well to castration (t=−4.211, p<.0001, and z=3.994, p<.0001 respectively). Our in vitro studies show that DHT increases localization of NLK in nucleoli of LNCaP. NLK levels in nucleoli negatively correlate with levels of nucleophosmin, a protein involved in regulation of proliferation, in the xenografts and in LNCaP cells in vitro. Interestingly we have also shown that in vitro NLK stimulates wnt signaling in LNCaP cells and this effecst in dependent on expresison of androgen receptor. In summary our data show that NLK expression is altered during prostate cancer progression and that NLK alters androgen receptor and wnt signaling pathways. Further studies to investigate mechanisms of NLK effects and NLK involvement in response to androgen ablation in prostate cancer are ongoing. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1937. doi:10.1158/1538-7445.AM2011-1937

Relaxin drives Wnt signaling through upregulation of PCDHY in prostate cancer

Relaxin, a potent peptide hormone of the insulin-like family normally produced and secreted by the human prostate, is upregulated in castrate resistant prostate cancer progression. In various tissues, relaxin increases angiogenesis and cell motility through upregulation of vascular endothelial growth factor, matrix metalloproteases, and nitric oxide, and therefore maybe an attractive target for cancer therapeutics. To examine the role of relaxin in prostate cancer progression, LNCaP cells stably transfected with relaxin (LNCaP(RLN)) were used to form xenograft tumors, and microarray expression analysis was subsequently performed to determine novel pathways regulated by relaxin. Prostate cancer tissue microarrays from patient samples were stained by immunohistochemistry for further validation and correlation of the findings. Expression analysis identified novel relaxin regulated pathways, including the ProtocadherinY (PCDHY)/Wnt pathway. PCDHY, which upregulates Wnt11, has previously been shown to stabilize beta-catenin, causing beta-catenin to translocate from the cytoplasmic membrane to the nucleus and initiate TCF-mediated signaling. LNCaP(RLN) xenografts exhibit increased PCDHY expression and increased cytoplasmic localization of beta-catenin, suggesting relaxin directs Wnt11 overexpression through PCDHY upregulation. Similarly, prostate cancer samples from patients who have undergone androgen ablation have increased Wnt11 expression, which is further upregulated in castrate resistant tissues. Like relaxin, Wnt11, and PCDHY are negatively regulated by androgens, and further analysis indicated that the overexpression of relaxin results in dysregulation of androgen-regulated genes. These data suggest that prostate cancer cell motility and altered androgen receptor activity attributed to relaxin may be mediated in part by Wnt11.

Gestational and neonatal‐onset hypothyroidism alters androgen receptor status in rat prostate glands at adulthood

Infertility associated with congenital and early childhood hypothyroidism is an important reproductive health problem in men. Nevertheless, the exact mechanism underlying hypothyroidism-induced changes in the prostate gland, an androgen-dependent organ that contributes a significant portion of the seminal plasma remains obscure. The present study tested the hypothesis "transient gestational- or neonatal-onset hypothyroidism may have duration dependent and lobe specific effect on androgen receptor (AR) status in the prostate glands of adult rats." Hypothyroidism was induced in pregnant and lactating rats by feeding 0.05% methimazole (MMI) through drinking water during fetal and neonatal milestones of testicular and prostatic development. Pregnant dams had MMI exposure from 9th day post-coitum (dpc) to 14 dpc (group II) or 21 dpc (group III). Lactating mothers had MMI exposure from day 1 post-partum (dpp) to 14 dpp (group IV) or up to 29 dpp (group V). AR status in the dorsolateral and ventral prostate lobes (DLP and VP) of the pups was assessed by RT-PCR, western blot and radio receptor assay. AR mRNA expression consistently decreased in the DLP of all groups, whereas it increased in VP of group III and V rats. AR protein consistently decreased in both DLP and VP of all experimental rats. AR nuclear ligand-binding activity diminished in groups II and IV, whereas it increased in groups III and V. The results obtained support the proposed hypothesis and indicate that an optimum thyroid activity during pre- and neonatal period determines AR status in the prostate glands at adulthood.

Proceedings of the Summit on Environmental Challenges to Reproductive Health and Fertility: executive summary

The 2007 Summit on Environmental Challenges to Reproductive Health and Fertility convened scientists, health care professionals, community groups, political representatives, and the media to hear presentations on the impact of environmental contaminants on reproductive health and fertility, and to discuss opportunities to improve health through research, education, communication, and policy. Environmental reproductive health focuses on exposures to environmental contaminants, particularly during critical periods of development, and their potential effects on future reproductive health, including conception, fertility, pregnancy, adolescent development, and adult health. Approximately 87,000 chemical substances are registered for commercial use in the United States, with ubiquitous human exposures to environmental contaminants in air, water, food, and consumer products. Exposures during critical windows of susceptibility may result in adverse effects with lifelong and even intergenerational health impacts. Effects can include impaired development and function of the reproductive tract and permanently altered gene expression, leading to metabolic and hormonal disorders, reduced fertility and fecundity, and illnesses such as testicular, prostate, uterine, and cervical cancers later in life. This executive summary reviews effects of pre- and postnatal exposures on male and female reproductive health, and provides a series of recommendations for advancing the field in the areas of research, policy, health care, and community action.

Proceedings of the Summit on Environmental Challenges to Reproductive Health and Fertility: executive summary

The 2007 Summit on Environmental Challenges to Reproductive Health and Fertility convened scientists, health care professionals, community groups, political representatives, and the media to hear presentations on the impact of environmental contaminants on reproductive health and fertility, and to discuss opportunities to improve health through research, education, communication, and policy. Environmental reproductive health focuses on exposures to environmental contaminants, particularly during critical periods of development, and their potential effects on future reproductive health, including conception, fertility, pregnancy, adolescent development, and adult health. Approximately 87,000 chemical substances are registered for commercial use in the United States, with ubiquitous human exposures to environmental contaminants in air, water, food, and consumer products. Exposures during critical windows of susceptibility may result in adverse effects with lifelong and even intergenerational health impacts. Effects can include impaired development and function of the reproductive tract and permanently altered gene expression, leading to metabolic and hormonal disorders, reduced fertility and fecundity, and illnesses such as testicular, prostate, uterine, and cervical cancers later in life. This executive summary reviews effects of pre- and postnatal exposures on male and female reproductive health, and provides a series of recommendations for advancing the field in the areas of research, policy, health care, and community action.

PSA/KLK3 AREI promoter polymorphism alters androgen receptor binding and is associated with prostate cancer susceptibility

The proximal promoter of the kallikrein-related peptidase 3 gene (KLK3/PSA) contains a single-nucleotide polymorphism (G-158A) located within the second canonical half-site for the prostate-specific antigen (PSA) androgen response element 1 (AREI). Previous studies suggest that this polymorphism may be associated with higher PSA levels and increase prostate cancer risk. We have investigated the potential functional significance of this polymorphism and its association with prostate cancer susceptibility by genotyping the G-158A polymorphism in 209 men diagnosed with prostate cancer and 223 healthy control men in an Australian Caucasian population. Functional analyses of PSA AREI demonstrated that the A allele increased binding of AREI to the androgen receptor, as well as increasing transcriptional response to androgens. Association studies of the G-158A polymorphism demonstrated that men with an A/A genotype had a 3-fold increased risk for developing prostate cancer [95% confidence intervals (CIs) = 1.36-6.52] and men with an A/G genotype had a 2.4-fold increased risk (95% CIs = 1.23-4.81). Under a dominant model, the A allele conferred a 2.6-fold increased risk for prostate cancer (95% CIs = 1.37-4.96, P = 0.004). Taken together with the finding that the G-158A polymorphism is associated with an increased risk of prostate cancer in Australian men, our functional data suggest that the presence of the A allele in AREI may, in part, account for the altered PSA regulation seen in prostate cancer.

618 POSTER A novel tyrosine kinase inhibitor exhibits significant anti-proliferative/pro-apoptotic effects in non-small cell lung cancer models

Prostate cancer (CaP) bone metastasis is an early event that remains inactive until later-stage progression. Reduced levels of circulating androgens, due to andropause or androgen deprivation therapies, alter androgen receptor (AR) coactivator expression. Coactivators shift the balance towards enhanced AR-mediated gene transcription that promotes progression to androgen-resistance. Disruptions in coregulators may represent a molecular switch that reactivates latent bone metastasis. Changes in AR-mediated transcription in androgen-sensitive LNCaP and androgen-resistant C4-2 cells were analyzed for AR coregulator recruitment in co-culture with Saos-2 and THP-1. The Saos-2 cell line derived from human osteosarcoma and THP-1 cell line representing human monocytes were used to display osteoblast and osteoclast activity. Increased AR activity in androgen-resistant C4-2 was due to increased AR expression and SRC1/TIF2 recruitment and decreased SMRT/NCoR expression. AR activity in both cell types was decreased over 90% when co-cultured with Saos-2 or THP-1 due to dissociation of AR from the SRC1/TIF2 and SMRT/NCoR coregulators complex, in a ligand-dependent and cell-type specific manner. In the absence of androgens, Saos-2 decreased while THP-1 increased proliferation of LNCaP cells. In contrast, both Saos-2 and THP-1 decreased proliferation of C4-2 in absence and presence of androgens. Global changes in gene expression from both CaP cell lines identified potential cell cycle and androgen regulated genes as mechanisms for changes in cell proliferation and AR-mediated transactivation in the context of bone marrow stroma cells.

Stress Kinase Signaling Regulates Androgen Receptor Phosphorylation, Transcription, and Localization

Activation of signal transduction kinase cascades is known to alter androgen receptor (AR) activity, but the molecular mechanisms are still poorly defined. Here we show that stress kinase signaling regulates Ser 650 phosphorylation and AR nuclear export. In LNCaP prostate cancer cells, activation of either MAPK kinase (MKK) 4:c-Jun N-terminal kinase (JNK) or MKK6:p38 signaling pathways increased Ser 650 phosphorylation, whereas pharmacologic inhibition of JNK or p38 signaling led to a reduction of AR Ser 650 phosphorylation. Both p38alpha and JNK1 phosphorylated Ser 650 in vitro. Small interfering RNA-mediated knockdown of either MKK4 or MKK6 increased endogenous prostate-specific antigen (PSA) transcript levels, and this increase was blocked by either bicalutamide or AR small interfering RNA. Stress kinase inhibition of PSA transcription is, therefore, dependent on the AR. Similar experiments involving either activation or inhibition of MAPK/ERK kinase:ERK signaling had little effect on Ser 650 phosphorylation or PSA mRNA levels. Ser 650 is proximal to the DNA binding domain that contains a nuclear export signal. Mutation of Ser 650 to alanine reduced nuclear export of the AR, whereas mutation of Ser 650 to the phosphomimetic amino acid aspartate restored AR nuclear export. Pharmacologic inhibition of stress kinase signaling reduced wild-type AR nuclear export equivalent to the S650A mutant without affecting nuclear export of the S650D mutant. Our data suggest that stress kinase signaling and nuclear export regulate AR transcriptional activity.

Role of SRC-1 in the Promotion of Prostate Cancer Cell Growth and Tumor Progression

Prostate cancer is initially androgen dependent and there is evidence that androgen receptor continues to play a role in androgen-independent prostate cancer. Androgen receptor activity depends both on the level of androgens and on the level of coactivators that interact with androgen receptor. Our goal was to evaluate the role of the androgen receptor coactivator SRC-1 in prostate cancer progression. Using tissue arrays to measure SRC-1 protein levels, we found that increased SRC-1 expression in clinically localized, androgen-dependent cancer is associated with clinical and pathologic variables of increased tumor aggressiveness. Interestingly, there was variable expression of SRC-1 in normal prostate tissue which correlated with the staining intensity of the corresponding cancer tissue. To test the contribution of SRC-1, we examined its role in androgen-dependent LNCaP and androgen-independent C4-2 prostate cancer cell lines. Using small interfering RNA to reduce expression of androgen receptor, we found that androgen receptor was required both for cell growth and for basal expression of prostate-specific antigen in the androgen-independent C4-2 cell line. Thus, although the cells can grow in an androgen-depleted medium, they remained androgen receptor dependent. Reduction of SRC-1 expression significantly reduced growth and altered androgen receptor target gene regulation in both LNCaP and C4-2 cell lines whereas it had no effect on the growth of the androgen receptor-negative PC-3 and DU145 prostate cancer cell lines. Although the requirement for androgens and androgen receptor in the development of prostate cancer is well established, our study implicates enhanced androgen receptor activity through elevated expression of SRC-1 in the development of more aggressive disease in men with prostate cancer.

Altered transcriptional regulation in cells expressing the expanded polyglutamine androgen receptor.

Kennedy's disease is a degenerative disease of motor neurons in which the causative mutation is expansion of a CAG/polyglutamine tract near the 5' end of the androgen receptor gene. The mutant protein misfolds, aggregates, and interacts abnormally with other proteins, leading to a novel, toxic gain of function and an alteration of normal function. We used a cell culture model to explore the mechanisms underlying the alterations in androgen receptor function conferred by the mutation. Here we show that cells expressing the wild-type androgen receptor with 24 CAG repeats respond to ligand by showing trophic effects including prolonged survival in low serum, whereas cells expressing the mutant receptor with 65 CAG repeats do not show a robust trophic response. This partial loss of function correlates with decreased levels of the mutant protein due to its preferential degradation by the ubiquitin-proteasome pathway. Expression analysis using oligonucleotide arrays confirms that the mutant receptor has undergone a partial loss of function, and fails to regulate a subset of genes whose expression is normally affected by ligand activation of the wild-type receptor. The mutant receptor has also undergone several functionally important post-translational modifications in the absence of ligand that the wild-type receptor undergoes in the presence of ligand, including acetylation and phosphorylation. These modifications correlate with a ligand-independent gain of function exhibited by the mutant receptor in expression analysis. Our findings suggest that polyglutamine expansion alters androgen receptor function by promoting its degradation and by modifying its activity as a transcription factor.

Androgen Receptor Phosphorylation: REGULATION AND IDENTIFICATION OF THE PHOSPHORYLATION SITES

Activation of signal transduction kinase cascades has been shown to alter androgen receptor (AR) activity. Although it has been suggested that changes in AR phosphorylation might be directly responsible, the basal and regulated phosphorylations of the AR have not been fully determined. We have identified the major sites of AR phosphorylation on ARs expressed in COS-1 cells using a combination of peptide mapping, Edman degradation, and mass spectrometry. We describe the identification of seven AR phosphorylation sites, show that the phosphopeptides seen with exogenously expressed ARs are highly similar to those seen with endogenous ARs in LNCaP cells and show that specific agonists differentially regulate the phosphorylation state of endogenous ARs in LNCaP prostate cancer cells. Treatment of LNCaP cells with the synthetic androgen, R1881, elevates phosphorylation of serines 16, 81, 256, 308, 424, and 650. Ser-94 appears constitutively phosphorylated. Forskolin, epidermal growth factor, and phorbol 12-myristate 13-acetate increase the phosphorylation of Ser-650. The kinetics of phosphorylation of most sites in response to hormone or forskolin is temporally delayed, reaching a maximum at 2 h post-stimulation. The exception is Ser-81, which continues to display increasing phosphorylation at 6 h. These data provide a basis for analyzing mechanisms of cross-talk between growth factor signaling and androgen in prostate development, physiology, and cancer.

Peripubertal exposure to the antiandrogenic fungicide, vinclozolin, delays puberty, inhibits the development of androgen-dependent tissues, and alters androgen receptor function in the male rat.

Vinclozolin is a well-characterized antiandrogenic fungicide. It produces adverse effects when administered during sexual differentiation, and it alters reproductive function in adult male rats by acting as an androgen-antagonist. Two active metabolites of vinclozolin, M1 and M2, compete with natural androgens for the rat and human androgen receptors (ARs), an effect that blocks androgen-induced gene expression in vivo and in vitro. In addition to their effects during perinatal life, androgens play a key role in pubertal maturation in young males. In this regard, the present study was designed to examine the effects of peripubertal oral administration of vinclozolin (0, 10, 30, or 100 mg kg-1 day-1) on morphological landmarks of puberty, hormone levels, and sex accessory gland development in male rats. In addition, as binding of the M1 and M2 to AR alter the subcellular distribution of AR by inhibiting AR-DNA binding, we examined the effects of vinclozolin on AR distribution in the target cells after in vivo treatment. We also examined serum levels of vinclozolin, M1, and M2 in the treated males so that these could be related to the effects on the reproductive tract and AR distribution. Vinclozolin treatment delayed pubertal maturation (at 30 and 100 mg kg-1 day-1) and retarded sex accessory gland and epididymal growth. Serum luteinizing hormone (LH; significant at all dosage levels) and testosterone and 5 alpha-androstane, 3 alpha, 17 beta-diol (at 100 mg kg-1 day-1) levels were increased. Testis size and sperm production, however, were unaffected. It was apparent that these effects were concurrent with subtle alterations in the subcellular distribution of AR. In control animals, most AR were in the high salt cell fraction, apparently bound to the natural ligand and DNA. Vinclozolin treatment reduced the amount of AR in the high salt (bound to DNA) fraction and it increased AR levels in the low salt (inactive, not bound to DNA) fraction. M1 and M2 were found in the serum of animals from the two highest dosage groups, but they were present at levels well below their K1 values. In summary, these results suggest that when the vinclozolin metabolites occupy a small percentage of AR in the cell, this prevents maximal AR-DNA binding and alters in vivo androgen-dependent gene expression and protein synthesis, which in turn results in obvious alterations of morphological development and serum hormone levels. It is noteworthy that similar exposures during prenatal life result in a high incidence of malformations in male rats.

Peripubertal exposure to the antiandrogenic fungicide, vinclozolin, delays puberty, inhibits the development of androgen-dependent tissues, and alters androgen receptor function in the male rat

Peripubertal exposure to the antiandrogenic fungicide, vinclozolin, delays puberty, inhibits the development of androgen-dependent tissues, and alters androgen receptor function in the male rat

Control of LNCaP proliferation and differentiation: actions and interactions of androgens, 1alpha,25-dihydroxycholecalciferol, all-trans retinoic acid, 9-cis retinoic acid, and phenylacetate.

There is increasing evidence that growth and differentiation of prostatic carcinoma cells may be modulated not only by androgens and growth factors but also by vitamin D, retinoids, and phenylacetate (PA). The latter agonists may have a role in the prevention and therapy of prostate cancer but their exact therapeutic potential remains unclear. Since both retinoids and vitamin D act via nuclear receptors, the same way androgens do, we studied the interactions of these compounds with androgen-induced proliferation and differentiation using LNCaP cells as a model of androgen-responsive tumor cells. PA was included because of its suspected different mode of action [H3]-thymidine incorporation was used as a measure of proliferative activity, secretion of prostate-specific antigen (PSA) as a measure of differentiated function. The present data show that 1alpha,25-dihydroxycholecalciferol (VD3), all-trans retinoic acid (atRA), 9-cis retinoic acid (9cRA), and PA stimulated LNCaP cell-differentiated function in the presence or absence of androgens. The effects on cell growth were more complicated. In the absence of androgens growth stimulatory effects were observed for the retinoids and under some conditions for VD3. These effects were limited, however, and tended to be more pronounced at low cell densities. In the presence of androgens nearly exclusively growth inhibitory effects were observed. On a molar basis VD3 was the most effective antiproliferative agonist (ED50 = 10(-9) M). It completely neutralized the stimulatory effects of androgens. Growth inhibition was not due to a decrease in the concentration of androgen receptor: whereas atRA, 9cRA, and PA did not alter androgen receptor levels, VD3 provoked a twofold increase. Neither in the presence nor in the absence of androgens did we observe any cooperativity in the growth stimulatory or inhibitory effects of VD3, atRA, or 9cRA. To test whether treatment with any of the studied agonists resulted in a phenotypic reversion and sustained growth arrest, LNCaP cells were pretreated with VD3, atRA, 9cRA, or PA for 6-12 days and reseeded at equal densities as untreated cells. In all cases tested [3H]-thymidine incorporation was restored within 6 days suggesting that none of these compounds caused irreversible growth inhibition.

The androgen receptor: a mediator of diverse responses.

Androgens mediate a number of diverse responses through the androgen receptor, a 110 kD ligand-activated nuclear receptor. Androgen receptor expression, which is found in a variety of tissues, changes throughout development, aging, and malignant transformation. The androgen receptor can be activated by two ligands, testosterone and dihydrotestosterone, which bind to the androgen receptor with different affinities. This difference in binding affinity results in different levels of activation of the androgen receptor by the two ligands. The androgen receptor acts as a transcriptional modifier of a variety of genes by binding to an androgen response element. The ability to confer androgen specific actions by the androgen response element may depend on other cell-specific transcription factors and cis-acting DNA elements in close proximity to it. Testosterone and dihydrotestosterone appear to act upon an identical nuclear receptor. However, in certain instances, they mediate different physiologic responses. For example, dihydrotestosterone, but not testosterone, is capable of mediating full sexual development of the male external genitalia. In some cases, the androgen receptor may induce opposite physiologic responses in similar tissue types depending on their location. For example, in male pattern baldness, activated androgen receptors may suppress the growth of distinct hair follicle populations through initiating stromal-epithelial actions, whereas other hair follicles continue to proliferate. In other cases, altered androgen receptor activity due to its mutation or altered expression may lead to pathology such as recurrence of prostate cancer due to development of androgen independence allowing tumor cell proliferation under androgen deprivation.

Androgen regulation of gene expression in the Syrian hamster Harderian gland

The androgenic control of sexual dimorphism has been studied in the Harderian gland from Syrian hamster and compared to rat Harderian gland, a system without dimorphism. Hybridization in situ with a rat cDNA clone has revealed the presence of androgen receptor mRNA in all secretory cells from male and female hamster glands. Testosterone or 5-α-dihydrotestosterone administration to females both caused a 60% decrease in the levels of 5-aminolevulinate synthase mRNA after 1 day of treatment, but the resulting patterns of in vitro translation using RNA from glands treated with the two androgens are different. Testosterone alters the mRNA levels for androgen receptor and 5-aminolevulinate synthase in the glands only 6 h after its implantation in females, and the action is maintained up to 10days of treatment. Finally, androgen administration to females or deprivation in males alter androgen receptor but not 5-aminolevulinate synthase mRNA levels in rat Harderian glands. Our results suggest that the androgen receptor from Harderian glands is responsible for the sexual dimorphism found in Syrian hamsters, whereas the lack of sexual dimorphism in rat seems to be due to a restricted effect of androgens in the glands.

The effect of chronic ingestion of selected pesticides upon rat ventral prostate homeostasis

The ability of the pesticides carbofuran, chlordane, diazinon, heptachlor, methoxychlor, and parathion to diminish 5α-dihydrotestosterone binding to rat ventral prostate cytoplasmic and nuclear androgen receptors was evaluated by in vitro studies. Only parathion and diazinon consistently inhibited 5α-dihydrotestosterone binding to ventral prostate cytoplasmic or nuclear androgen receptors, the remaining pesticides being relatively ineffective. The data suggested that only parathion and diazinon should be able to affect prostate homeostasis via a mechanism involving altered androgen receptor function. After 90 days of pesticide ingestion, ventral prostate androgen receptor homeostasis was altered in all the rats. Significantly, receptor homeostasis was least affected in diazinon- and parathion-fed rats, whereas ingestion of carbofuran or chlordane produced the most profound changes. Methoxychlor ingestion diminished prostate size and cell content. Carbofuran, chlordane, and parathion, but not heptachlor or diazinon, altered ventral prostate RNA metabolism without affecting cell content. Since pesticide ingestion did not alter mean plasma testosterone concentration, changes in both androgen receptor and prostate homeostasis could be attributed to pesticide action principally occurring in the ventral prostate. The absence of a correlation between pesticide inhibition of 5α-dihydrotestosterone binding to prostate androgen receptors and the pesticide's capacity to alter prostate homeostasis demonstrated inhibition studies to be ambiguous predictors of pesticide action in the ventral prostate.