Follicular Steroidogenesis: Effect of Reproductive Condition

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Abstract
Follicular steroidogenesis has been investigated extensively in nonpregnant animals. To determine 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 (15PSP)] and pregnant (P) [Days 7 (7P), 15 (15P) and 28 (28P)] 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 min intervals and assayed for progesterone (P4), testosterone (T) and estradiol-17β (E). Steroid concentrations are expressed as pg/follicle/20 min. The secretion of P4 by unstimulated 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 (P4 for NP was 0.21 ng/ml, whereas PSP and P rabbits had concentrations ranging from 6.83 to 17.86 ng/ml. Luteal P4 content was not significantly different for any groups, varying from 77.4 to 161.3 ng/mg protein.