Prolactin interacts with gonadotropin through a suppression of c-AMP production probably as a LH-sensitive adenylate cyclase inhibitor.
The interaction between gonadotropin and prolactin (PRL) on ovarian steroidogenesis as well as c-AMP production was studied in rat ovaries. Ovaries obtained from adult female Wistar rats in a morning of proestrus were chopped into 30-40 pieces and subjected to short term incubation studies using various buffers. HCG-stimulated c-AMP, estradiol (E2), progesterone (P) secretions were suppressed in a dose-dependent manner by ovine (o) PRL in a plain Gey-Gey (G-G) buffer. Addition of 3-isobutyl-1-methyl-xanthine (IBMX) increased c-AMP accumulation as well as E2 and P secretions. Deletion of Ca++ from the IBMX buffer stimulated c-AMP production, but suppressed steroid secretion. The inhibitory effect of PRL on E2 and P was not demonstrated in IBMX buffer at any Ca++ concentration examined despite suppression of c-AMP production. In conclusion, it was demonstrated that PRL inhibited gonadotropin-stimulated production of E2 and P by inhibiting c-AMP production. IBMX stimulated accumulation of c-AMP, E2 and P and counteracted with the antigonadal effect of PRL. Ca++ inhibited c-AMP accumulation but stimulated E2 and P secretions. The data suggested that PRL exerts its antigonadal effect through an inhibition of adenylate cyclase action in a manner similar to that of Ca++.
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000067956:Adenylyl Cyclase Inhibitors; D000818:Animals; D006063:Chorionic Gonadotropin / Q000494:pharmacology*; D000242:Cyclic AMP / Q000378:metabolism*; D004958:Estradiol / Q000378:metabolism*; D005260:Female; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D010053:Ovary / Q000187:drug effects / Q000378:metabolism*; D011374:Progesterone / Q000378:metabolism*; D011388:Prolactin / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains
D000067956:Adenylyl Cyclase Inhibitors; D006063:Chorionic Gonadotropin; D011374:Progesterone; D004958:Estradiol; D011388:Prolactin; D000242:Cyclic AMP; D015056:1-Methyl-3-isobutylxanthine