REGULATION OF FOLLICULAR LUTEINIZATION BY AN AGONIST OF GONADOTROPIN-RELEASING-HORMONE (GNRH)

Long treatments with GnRH agonist are used in patients to suppress the endogenous secretion of gonadotropins, however; these analogs have a direct effect on the ovary. The aim of this work was to study the in v ivo effect of the GnRH analogue, leuprolide acetate (LA) on ovarian st eroidogenesis and apoptosis mechanisms. LA (1 mu g/rat/day) was inject ed to PMSG/hCG superovulated rats. Corpora lutea were isolated by micr odissection and incubated (4/0.5 mt) during 3 h with LH (10 ng/ml)or d ibutyryl cAMP (dcAMP 1 mM). Progesterone production was measured obser ving in LA treated rats a decrease in basal and LH stimulated values ( Basal = Control C: 96.6 +/- 9.6; LA: 22.9 +/- 2.8; LH= C: 145.7 +/- 4. 9; LA: 23.6 +/- 2.0 ng/ml, p<0,001). In contrast, dcAMP stimulated sig nificantly both groups (C: 153.9 a 11.8; LA: 83.15 +/- 8.2). cAMP prod uction was lower in LA corpora lutea and LH was not able to stimulate them (Basal= C: 7.29 +/- 1.6; LA: 1.17 +/- 0.6; LH= C: 13.2 +/- 0.4; L A: 2.5 +/- 0.4 ng/ml, p < 0.01). Corpus luteum of both groups showed s imilar protein content. On the other hand, taking into account that in ovarian histological slides of LA treated rats we observed more atres ic follicles and less corpora lutea, we determined the amount of apopt otic cells. The criterion used was the presence of apoptotic bodies an d nuclear chromatin aggregated in dense masses beneath the nuclear env elope. An increase of apoptotic cells in the LA group ovaries was dete cted. This result was confirmed by immunohistochemical technics (TUNEL ). It was concluded that LA treatment produces in ovarian cells a fail ure in the LH receptor-adenilate cyclase system and an increase in cel lular apoptosis.