Inhibition of luteinizing hormone receptor expression during the development of caprine corpora lutea by administration of gonadotropin-releasing hormone antagonist.

The present study was conducted to examine effects of a potent GnRH antagonist (GA), which suppresses release of luteinizing hormone (LH), on LH receptor expression during the development of the caprine corpus luteum (CL). Goats were divided into control and GA-treated groups. The goats were treated with saline or GA (50 microg/kg, s.c.) on days 0 (day of ovulation), 4 and 8 (control only), and CL collected on a subset of goats (n = 3 for each day) on days 0 (no saline), 4, 8, or 14 (control only). Ribonuclease protection assay and [(125)I]-hCG binding assay were performed to quantitate mRNA and protein of the LH receptor in the CL, respectively. On day 4, CL weight, levels of LH receptor mRNA and protein in the GA-treated group were similar to those of the control group. By day 8, CL weight and levels of LH receptor mRNA and protein in the GA-treated group were reduced relative to those of the control group (P < 0.05). There was no difference of affinity of the LH receptor between both groups on day 8. These results suggest that the treatment with GA inhibits gene and protein expressions of the LH receptor during the development of CL in the goat, and thus, support an idea that endogenous LH participates in the increase of its own receptor. Copyright 2002 Wiley-Liss, Inc.