Follicular steroidogenesis: Effect of reproductive condition

Follicular steroidogenesis has been investigated extensively in nonpregnant animals. To deter-mine if follicular steroidogenesis is altered during pseudopregnancy or pregnancy, large Graafian follicles (1.5-2.0 mm) were isolated from nonpregnant (NP), pseudopregnant (PSP) Days 7 (7PSP) and 15 (I5PSP)l and pregnant (P) IDays 7 (7P), 15 (15P) and 28 (28P)l rabbits and placed in perifusion chambers. After the establishment of a basal steroid output, follicles were stimulated with LH (100 ng, NIH-S20):FSH (50 ng, 50.4 X NIH-FSH-S1; Papkoff). Samples were collected continuously at 20 mm intervals and assayed for progesterone (P4), testosterone (T) and estradiol-17a (E). Steroid concentrations are expressed as pg/follicle/20 mm. The secretion of P4 by un-stimulated follicles was similar for all groups; however, differences were observed after LH:FSH stimulation. With increasing length of PSP or P, follicles secreted significantly less P4. The values for NP, 7PSP and 7P were different (P<0.01) from those of 15PSP and 15P, and 15P was different from 28P (P<0.025), whereas E secretion by NP was greater (P<0.001) than for PSP and P groups. After treatment with LH:FSU, T and E secretion by NP was elevated (P<0.025) over PSP and P. There were no differences among PSP and P groups, except that stimulated follicles of 28P grou