Steroid Secretion by Ovarian Follicles of Rabbits in Different Reproductive States
Adenylyl cyclase (AC) activity of follicles of estrous rabbits (C) is greater than that of follicles of pseudopregnant (Ps) and pregnant (P) rabbits. To determine if there is a concomitant change in steroidogenesis and if the reproductive condition of the animal alters follicular steroid secretion, we removed follicles from C, Ps (7 or 15 days), or P (7, 15 or 28 days) rabbits and placed them in perifusion chambers. After the establishment of a baseline, LH (100 ng, NIH-S20; NIAMMD) and FSH (50 ng, 50.4 x NIH-FSH-SI; Papkoff) were injected into the chambers. The medium was assayed for progesterone (P4), testosterone (T), and estradiol-17β (E2). Steroid concentrations are expressed as pg/follicle/20 min. In the unstimulated follicles, T secretion (225) was similar for all groups except less for 15Ps and 28P (120;P< 0.025); E2 secretion by C (442) was greater (P< 0.001) than for Ps and P groups (164) which were all similar. After LH:FSH, T (4790) and E2 (910) secretion by C was elevated (P< 0.025) over Ps and P (T-2690; E2-319). There were no differences among Ps and P groups except that 28P secreted significantly less T than 15P (P< 0.05). P4 secretion by unstimulated follicles were similar for C, Ps, and P. After LH: FSH, differences were observed. With increasing length of pseudopregnancy or pregnancy, follicles secreted significantly less P4 (C-1046, 7Ps-755, 15Ps-448, 7P-885, 15P-561, 28P-360). C, 7Ps and 7P were different (P < 0.01) from 15Ps and 15P and 15P was different (P< 0.01) from 28P. These results indicate that follicles removed from rabbits in various reproductive states have different steroid profiles. Possibly high intragonadal P4 and circulating gonadotropins have a modulating effect on follicular steroidogenesis in Ps and P rabbits since AC activities are similar.
KeywordsAdenylyl Cyclase Corpus Luteum Ovarian Follicle Adenylyl Cyclase Activity Gonadotropin Stimulation
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