Molecular basis of gonadotrophin action on human granulosa cell function.

Abstract

We studied in vitro the effects of Follicle Stimulating Hormone (FSH) and Luteinising Hormone (LH) on: 1) mature human granulosa cell proliferation and steroidogenesis; 2) intra-cellular second messenger (cAMP) generation, and the effects of cAMP analogues on cell function; and 3) mRNA expression of the rate limiting enzymes for progesterone and oestradiol synthesis namely: Cholesterol side chain cleavage (P450 SCC), Aromatase (P450 Arom); and 4) LH receptor mRNA expression. FSH maintained or stimulated, whereas LH markedly inhibited, basal granulosa cell proliferation. Steroidogenesis (oestradiol and progesterone production) was dose dependently increased by both gonadotrophins; with LH having the greater effect. However, only LH was able to induce maximal progesterone production. FSH generated about ten fold less cAMP than LH; and low and high doses of cAMP analogue were able to mimic FSH and LH effects respectively. Northern analyses showed that both FSH and LH were able to induce maximal P450 Arom mRNA expression, whereas only LH could stimulate maximal P450 SCC mRNA transcription. Maximal P450 Arom mRNA expression was associated with less cAMP generation than for P450 SCC. LH-R mRNA expression was induced by FSH but the strongest stimulatory effect was with LH. These results indicate that: 1) FSH and LH have markedly different effects on mature granulosa cell function; 2) the differential action of FSH and LH are dose dependently mediated through intracellular cAMP; 3) mRNA expression of P450 SCC and P450 Arom are differentially regulated by gonadotrophins and intracellular cAMP; and 4) LH was the most potent inducer of its own receptor mRNA.(ABSTRACT TRUNCATED AT 250 WORDS)