Modulation of pituitary gonadotropins and prolactin secretion by testosterone in vitro

Abstract

Investigations were undertaken to study the differential modulation of LH, FSH and PRL secretion by testosterone (T) using whole pituitary (PI) or pituitary-hypothalamus coincubates (PHC) as in vitro constructs. PI and PHC from intact and castrated rats were incubated with or without T thrice, for 24 h each, (24 h x 3, total incubation period 72 h). The spent media was replenished every 24 h. At the end of 72 h, a few of the pituitary glands were challenged with 10 nM LHRH for 4 h. The spent media and pituitary glands were analyzed for LH, FSH and PRL using specific RIAs. Incubation of PI or PHC from intact rats with T stimulated the release of LH and FSH but inhibited the release of PRL. T had no effect on the intrapituitary contents of LH but inhibited intrapituitary contents of FSH and PRL, as compared to controls incubated without T. Castration increased intrapituitary contents of LH and FSH with concomitant decrease in PRL levels. Incubation of PI or PHC from castrated rats with T inhibited intrapituitary contents of LH to intact pituitary levels, while PRL levels were further reduced instead of being ameliorated. It is concluded that PI or PHC can be used as convenient in vitro models to monitor the effect of castration or of T modulation of pituitary and hypothalamus functions. T does not affect the synthesis of LH at the gonadotroph level but facilitates the regulation of intracellular LH and FSH levels. It is postulated that T inhibits the synthesis of FSH/PRL at the gonadotroph/lactotroph levels.

Effects of testosterone on hormonal content and calcium-dependent basal secretion in female rat pituitary cells

“…Onuma et al [43] found that 11-ketotestosterone could increase or decrease prolactin mRNA in female salmons depending on their reproductive stage. In parallel to our experiments with pituitary cells from female rats, the long-term negative effects of T treatment in vitro on basal prolactin synthesis and release from male pituitary cells have been reported [8,44]. Androgens may also exhibit a rapid stimulatory effect of T on type-2 lactotrophs; in these cells T enhances prolactin stimulation after 5 min, which points to a nongenomic effect of T [45].…”

“…On the other hand, conflicting data exist on the effects of T on other anterior pituitary cells [8,9]. It is furthermore unknown whether and how T affects basal (in the absence of agonist) hormone release in gonadotrophs and other anterior pituitary secretory cell types.…”

4-Nitro-3-phenylphenol has both androgenic and anti-androgenic-like effects in rats

“…This result indicated that PNMPP played a role in decreasing FSH and LH secretion via GnRH stimulation. As we known, AR is found in the pituitary and affected by androgen administration and castration [ 16 , 17 , 18 , 19 , 20 ]. Androgen also has a role in control of GnRH released from the hypothalamus, as shown by the effect of testosterone treatment on reducing GnRH mRNA [ 17 ] and GnRH release [ 18 ].…”

“…Androgen also has a role in control of GnRH released from the hypothalamus, as shown by the effect of testosterone treatment on reducing GnRH mRNA [ 17 ] and GnRH release [ 18 ]. In in vitro studies, androgen was found to suppress pituitary responsiveness to a hypothalamic extract and changed FSH and LH release from the anterior pituitary [ 20 , 21 ]. Androgen acts by binding at receptor sites and then has a negative feedback action that decreases FSH and LH secretions by slowing the GnRH pulse generator and suppressing FSH and LH syntheses in the pituitary [ 22 ].…”