Release of growth hormone, prolactin and somatostatin during perifusion of anterior pituitary and preoptic-medial basal hypothalamus from male and female rats.

These experiments were designed to determine whether it is possible using in vitro perifusion to identify a sex difference in anterior pituitary (AP) release of growth hormone (GH) and, if so, to determine whether this difference is correlated with a sex difference in hypothalamic release or content of somatostatin (SRIF). Age-matched rats of both sexes were decapitated at approximately 09.00 h, and blood was collected for determination of non-stress plasma concentrations of GH. Each pituitary was rapidly removed and prepared for perifusion of the AP, and each preoptic-medial basal hypothalamus (PO-MBH) was removed and placed in a separate perifusion chamber. The effluent fractions from perifused APs were assayed for GH and prolactin (Prl), and those from PO-MBH blocks were assayed for SRIF. Non-stress plasma GH concentrations were similar in males and females. During perifusion, baseline GH release was higher (P less than 0.001) from male than from female APs. Release of GH from the APs of both sexes was similarly inhibited (P less than 0.001) by a 1-h administration of SRIF (10(-7) M), and high K+ (50 mM) caused larger (P less than 0.05) GH responses from male than from female APs. In contrast, baseline Prl release was higher (P less than 0.01) from female than from male glands, and Prl release was not affected by SRIF. Male and female PO-MBH tissues showed similar baseline release of SRIF and similar responses to high K+. After perifusion, GH content and concentration were higher in APs from males than from females, but SRIF content in the perifused male and female PO-MBH tissues was similar.(ABSTRACT TRUNCATED AT 250 WORDS)