Seasonal and diurnal changes of prostatic androgen receptor and circulating testosterone in young mature rats

Abstract

Low- and high-salt (600 mM KCl) extractable androgen receptors were measured in the ventral prostate lobes of 70-day-old rats which were housed in constant environmental conditions (22 +/- 2 degrees C, 65 +/- 5% air humidity, light 6.00h-18.00h). Seasonal variations were observed during 2 years, exhibiting elevations in late summer and autumn and depressions in late winter and spring time. These fluctuations were superposed by steep changes from month to month. The maximum and minimum values of the low- and high-salt extractable receptors differed within 1 year by a factor 8.5 and 2.4, respectively. Both receptor fractions showed a diurnal rhythm as measured during 1 day in January with maximal concentrations at 9.00 h (low-salt: median = 1308 fmol/mg DNA) and minimal values at 18.00 (424) and 24.00 (230). The electrophoretic mobility in agar gel of pH 8.2 also showed a diurnal variation with maximal values at 18.00 h in either receptor fraction. Neither the seasonal nor the diurnal variations were correlated to the corresponding rhythms of serum testosterone concentrations. As steroid receptors may be regulated by neural transmission, in a final experiment the parasympathic innervation of the prostate was blocked by infiltrating the plexus pelvicus with a local anesthetic drug. One hour later, the total receptor concentration was not changed, while the ratio of low- to high-salt extractable receptors and the electrophoretic mobility of both fractions were elevated as compared to the control animals. This finding indicates that peripheral neural transmission rather than circulating testosterone may be involved in the regulation of androgen receptors in rat ventral prostate.

Androgen Regulates Follicle-Stimulating Hormone β Gene Expression in an Activin-Dependent Manner in Immortalized Gonadotropes

“…The physiological relevance of these combined opposing mechanisms are applicable both to nonseasonal animals like rats, which would require steady FSH levels to maintain spermatogenesis throughout the year, and to seasonal animals like sheep, in which seasonally increasing androgen levels could result in seasonal net increases in FSH and thereby dramatically increase spermatogenesis during the breeding season. Interestingly, FSH levels in male rats do not fluctuate substantially once maturity is reached, whereas both androgen and LH levels surge diurnally (48,58,59). In male sheep, androgen and FSH levels rise simultaneously at the beginning of the breeding season (60).…”

Cyclosporine Induces Progressive Attenuation of Baroreceptor Heart Rate Response and Cumulative Pressor Response in Conscious Unrestrained Rats

“…The lack of a change in serum testosterone level precludes a role for this hormone in the early (Ͻ5 days) attenuation of BRS caused by CsA in our study. Notably, to rule out any effect of diurnal variation in plasma testosterone levels, blood samples were withdrawn from all rats at a specified time on the 5th day (Moeller et al, 1988;Leal and Moreira, 1997).…”

“…Twenty minutes after the end of infusion, another baroreflex curve, completed in approximately 1 h, was constructed as described above. Each experiment lasted approximately 2.5 h. These procedures were repeated for five consecutive days and on the 5th day blood samples (0.6 ml) were collected from the femoral artery, for measurements of serum testosterone level at specified time, to avoid the daily variation of plasma testosterone (Moeller et al, 1988;Leal and Moreira, 1997).…”

“…CsA produces a rapid elevation in blood pressure (BP) that resembles the acute CsA-induced hypertension in humans (Moeller et al, 1988;Lyson et al, 1994). Although evidence suggests that the acute pressor response to CsA is sympathetically mediated (Moeller et al, 1988;Lyson et al, 1994), other findings argue against this possibility (Kaye et al, 1993;Stein et al, 1995). Nonetheless, whether the attenuation of BRS contributes to the acute pressor effect of CsA has not been investigated.…”

hormone nuclear receptor (EcR) exhibits circadian cycling in certain tissues, but not others, during development in Rhodnius prolixus (Hemiptera)

“…The expression and/or density of several of these nuclear hormone receptors has been shown to cycle with a daily rhythm in a small but growing number of reports and is presumed to reflect the rhythmic induction of the receptor by hormones, e.g. daily fluctuations have been reported for the expression of the oestrogen β receptor gene in rat suprachiasmatic nucleus (Wilson et al 2002), oestrogen receptors in rat liver Francavilla et al 1986), androgen receptors in rat liver ) and in rat prostate (Moeller et al 1988), 5-α-dihydrotestosterone receptor in rat pineal (Gupta et al 1993), thyroid hormone β1 receptor in liver (Doulabi et al 2002) and corticosteroid receptors in various rat tissues (Spencer et al 1993;Holmes et al 1995;Herman et al 1993;Kitchener et al 2004) and in equine peripheral blood mononuclear cells (Potla et al 1993). These reports are all descriptive accounts of changes in receptor expression or density within a single 24-h period and have not addressed whether these daily changes are under circadian control, i.e.…”