Ovarian steroids modulate the self-priming effect of luteinizing hormone-releasing hormone on bovine pituitary cells in vitro.

Abstract

LHRH has the ability to prime the anterior pituitary gland, thereby increasing the quantity of LH and FSH released by a standard dose of LHRH. This priming effect may play an important regulatory role in LH secretion. In experiments described herein, we demonstrate that LHRH priming occurs via a direct effect on bovine gonadotrophs and LHRH priming is modulated by ovarian steroids. Bovine pituitary cells were primed as follows: Medium was changed at time zero, then at 50-min intervals for 400 min. LHRH was added 10 min before each medium change, i.e. cells were exposed to LHRH for 10 min during each of eight consecutive 50-min incubations. At the end of this 400 min, the degree of priming was assessed by incubating the pituitary cells with 0 or 1 ng/ml LHRH for 4 h (test period). The first variable tested was priming dose of LHRH (0, 0.001, 0.01,0.1, or 1 ng/ml). In general, LHRH priming did not affect basal release of LH but did increase the ability of a test dose of LHRH to induce LH release. For exampl...