Effect of gonadotropin releasing hormone on ventral prostate of rat

Testosterone induced increase in ornithine decarboxylase (ODC) activity was inhibited by simultaneous treatment with gonadotropin releasing hormone (GnRH) and its analogue in the ventral prostate of rat. Inhibition of 3H-uridine, 3H-phenylalanine and 3H-leucine incorporation into TCA precipitable material was also inhibited by GnRH in the dihydrotestosterone (DHT) treated animals. These studies further confirm that GnRH acts directly on ventral prostate and causes inhibitory effects.     

Regional cellular heterogeneity and DNA synthetic activity in rat ventral prostate during postnatal development.

Previous studies have provided evidence that the rat ventral prostate grows primarily, if not exclusively, at its distal tips. However, as yet there have been no analyses in which individual cells in defined regions of the prostatic ductal system have been resolved and quantified. Moreover, the possibility that the prostate might grow differently at different times of postnatal development has received little attention. Our objectives were to identify and quantify the proliferating epithelial and stromal cells in defined regions of the rat ventral prostate during its postnatal development. To this end, 3H-thymidine was administered in vivo to rats of ages 10-60 days. A dissection technique was then used by which the distal, intermediate, and proximal segments of the prostatic ductal system were physically isolated from each other without removing the stromal tissue. Longitudinal sections of these segments were examined for cellular composition and DNA synthetic activity. Regional heterogeneity with respect to cell composition and cell proliferation was seen. In rats of all ages, DNA synthetic activity was seen in epithelial and stromal cells throughout the prostate, rather than only in the distal segment. At Days 10 and 20, significantly higher percentages of epithelial and stromal cells were labeled in the distal than in the proximal segments; but at Days 45 and 60, the percentages of labeled epithelial and stromal cells in the distal, intermediate, and proximal segments were similar. Thus, in all segments, and at all ages, substantial labeling was seen throughout the prostate. These data suggest that the prostate grows in both length and width throughout postnatal development, reminiscent of the growth of a tree.     

性激素对血红素氧化酶在大鼠前列腺腹侧叶表达的影响

血红素氧化酶(heme oxygenase,HO)是产生内源性一氧化碳(carbon monoxide,CO)的限速酶,最近发现内源性CO在调节平滑肌张力方面起重要作用。而人的良性前列腺增生(benign prostates hyperplasia,BPH)所致的膀胱出口梗阻与前列腺平滑肌张力有密切关系,但还不清楚内源性HO/CO系统是否介导了前列腺平滑肌的活动。为了观察性激素对大鼠前列腺腹侧叶中血红素氧化酶-1(heme oxygenase-1,HO-1)和血红素氧化酶-2(heme oxygenase-2,HO-2)基因表达的影响,我们采用睾丸切除术建立雄性SD大鼠去势模型,用RT-PCR方法观察HO-1和HO-2的转录水平,应用免疫组织化学结合图像分析技术,观察去势、外源性雄激素和雌激素对前列腺腹侧叶中HO—1和HO-2蛋白水平的影响。结果表明,HO-1和HO-2在正常大鼠前列腺腹侧叶中都有表达,腺上皮细胞和纤维平滑肌间质呈现HO-1的免疫活性,HO-2的免疫染色仅在腺上皮细胞内检测到;去势组HO-1的mRNA和蛋白表达水平显著低于正常对照组(P<0.01):外源性给予雄激素组和雌激素组的HO-1表达水平明显增高(P<0.01),且雌激素主要增加前列腺纤维平滑肌间质的HO-1表达:HO-2在各组间的表达无明显差异(P>0.05)。这些结果提示,性激素对HO-1有诱导作用,但对HO-2无明显的影响,因此推测一氧化碳-血红素氧化酶(CO—HO)     

Effects of isoproterenol on cyclic-AMP metabolism in rat ventral prostate.

Beta-Adrenergic stimulation of the ventral prostate cyclic-AMP system was investigated by examining the influence of isoproterenol on endogenous cyclic-AMP levels as well as on the activities of adenylate cyclase CEC 4.6.1.1) and cyclic-AMP-dependent and independent protein kinases (EC 2.7.1.37). Administration of isoproterenol (1 mg/kg, ip) resulted in rapid elevation of adenylate cyclase activity (119%) and cyclic-AMP levels (593%). The observed isoproterenol-stimulated changes in cyclic-AMP metabolism of the ventral prostate were time-dependent and maximal stimulation was seen 5 min after treatment with this beta-adrenergic agonist. The increases in prostatic adenylate cyclase and cyclic-AMP also were related to the dose of isoproterenol administered and maximal enhancement of these parameters was seen with 1 mg/kg dose of the agonist. Whereas pretreatment of rats with propranolol (3mg/kg, ip) partially reversed these alterations, administration of an alpha-adrenergic antagonist, phentolamine, even at a dose of 5 mg/kg, failed to elicit any appreciable effect. Stimulation of prostatic soluble protein kinase by isoproterenol was associated with a decrease (33%) in the activity of the cyclic-AMP-dependent protein kinase with a concomitant increase (25%) in that of the independent enzyme. Whereas the ability of the enzyme to bind cyclic-(3H) AMP in vitro was decreased (54%) following isoproterenol treatment, the protein kinase activity ratio (-cyclic-AMP/+cyclic AMP) was significantly elevated from 0.51+/0.05 to 0.95+/0.08. Although propranolol alone had little or no effect on these parameters, it inhibited partially the isoproterenol-induced alterations in cyclic-AMP-dependent protein kinase and the cyclic-AMP binding capacity. Treatment with propranolol also blocked the increases in the kinase activity ratio and in the activity of cyclic-AMP-independent enzyme seen with isoproterenol. Data suggest that the concentration of ventral prostate cyclic-AMP as well as the activities of adenylate cyclase and cyclic-AMP-dependent and independent form of protein kinases are subject to modulation by beta-adrenergic stimulation.     

Pneumadin in the rat ventral prostate and its hormonal regulation.

Pneumadin (PNM) is a decapeptide originally isolated from mammalian lungs, and exerts a potent antidiuretic action by stimulating arginine-vasopressin release. We have recently developed a sensitive and specific radioimmunoassay (RIA) for rat PNM and detected high concentrations of PNM--not only in the rat lungs, but also in the prostate. Hence, we investigated whether prostate PNM content is regulated by sex hormones. Male adult rats were orchidectomized or sham-operated and given a subcutaneous injection of testosterone or estradiol (40 and 5 mg/kg), respectively. The animals were decapitated one week after surgery, and their ventral prostates were promptly removed and weighed. PNM concentration and localization in the prostate were investigated by RIA and immunocytochemistry (ICC). Orchidectomy resulted in significant decreases in the prostate weight and PNM concentration, and testosterone administration prevented these effects. Estradiol administration to sham-operated rats caused prostate atrophy without changing PNM concentration. ICC localized PNM immunoreactivity (IR) exclusively in the epithelial cells of the ventral prostate. Orchidectomy markedly reduced PNM-IR concentration, while testosterone abolished this effect. Estradiol did not modify PNM-IR concentration in the atrophic prostate of sham-operated rats. We conclude that PNM content of rat prostate is dependent on the presence of adequate levels of circulating testosterone. The possibility that PNM plays a key role in the maintenance of the prostate growth is unlikely since estradiol-induced gland atrophy is not associated with any decrease in PNM concentration. The localization of PNM in the epithelial cells could suggest that this peptide may be involved in the regulation of some testosterone-dependent secretory functions of the rat prostate.     

Aging in the rat prostate. Reduction in detectable ventral prostate androgen receptor content.

Aging in the rat is associated with a reduction in the detectable androgen receptor content of the ventral prostate. The reduction in cytoplasmic receptor content did not appear to be attributable to an aging-associated production of a receptor-inactivating factor or to an aging-associated change in the sedimentation properties of the androgen receptor of young and aged animals.Saturation analysis of cytoplasmic extracts prepared from two different breeds of similar albino rats and a genetically distinct strain of inbred brown rats demonstrated quantitative aging-associated reductions in the androgen-receptor content per cell of the ventral prostate. The reduction in receptor content per cell appeared to increase progressively in magnitude with increasing age. The mean value for the cytoplasmic androgen receptor sites per cell for the oldest animals (mean age 884 days) was only 14% of the mean value for the young mature animals (mean age 185 days) of the same breed. The binding affinities of the detectable androgen receptor of the young mature and aged animals were essentially identical. This observation does not eliminate the possibility that the observed reduction results from an aging-associated production of defective receptor. Evaluation of the total DNA content of the ventral prostate did not provide evidence for an aging-associated selective loss of receptor-containing cells. These data in toto were consistent with the interpretation that aging is associated with a mean reduction in the androgen-receptor content per receptor-containing cell.Both cytoplasmic and nuclear androgen retention were evaluated in vivo. These experiments provided qualitative confirmation of the in vitro saturation analyses as there was a highly significant aging-associated reduction in the amount of androgen specifically bound by these prostatic compartments. Total specific androgen retention by the ventral prostate of aging adults was reduced by 55% relative to young mature animals. This result was nearly identical to that obtained for the same breed and age category of animals when evaluated by in vitro saturation analysis.Preliminary in vitro experiments revealed a diminution in the uptake of androgen receptor by purified nuclei from aged animals relative to purified nuclei from young mature animals. The magnitude of the diminution in nuclear acceptor capacity was insufficient to account for the reduction in nuclear retention of androgen determined in vivo. The data were consistent with the interpretation that the cytoplasmic receptor is the major determinant of nuclear androgen retention in the ventral prostate.     

Effect of glucose on the major testosterone-maintained protein in the cultured rat ventral prostate

The effect of glucose on the androgen-maintained protein synthesis was studied in the cultured rat ventral prostate. The expiants were cultivated for 5 days in the glucose-free medium containing 10% fetal calf serum with or without 10 mM glucose and 10⁻⁷M testosterone. In some experiments tunicamycin, a specific inhibitor of protein glycosylation was added to the glucose-containing medium. The morphological integrity of the tissue was maintained in all the mediums used. At the end of the culture, the expiants were incubated with [³⁵S]methionine. Soluble radioactive proteins were separated by the SDS-polyacrylamide gel electrophoresis and analyzed further by the fluorography. Glucose was necessary for the testosterone-maintained accumulation of three components (M_r less than 14,000) of the major prostatic secretory protein. The electrophoretic migration, glycosylation pattern and immunological data (not shown) indicated that it was the well-known prostatic binding protein. On the other hand, two prominent polypeptides (M_r 70,000 and 100,000) appeared in the absence of glucose. Glucose starvation and the inhibition of glycosylation with tunicamycin caused similar effects on the labelling of the newly-synthesized soluble proteins. The mechanisms of glucose maintenance of the major prostatic protein and suppression of two high molecular weight proteins seemed to be different, although glycosylation was probably involved in both glucose effects.     

Effect of clofibrate on the CoA thioester profile in rat liver.

Acute and chronic treatment with clofibrate increased the total CoA content of rat liver and altered the profile of the various CoA thioesters. There resulted a 2–3 fold increase in the contents of long chain acyl CoA, acetyl CoA and free CoA, contrasting with significant decreases found in succinyl CoA, malonyl CoA and acetoacetyl CoA contents. It is postulated that the known increase in fatty acid binding protein and/or the increased extramitochondrial β-oxidation of fat by an increased peroxisomal population may direct the compartmentation and metabolic fate of fatty acids and their CoA derivatives following clofibrate treatment.