Simultaneous measurement of steroids in follicular fluid and ovarian venous blood in the rabbit.

Steroid concentrations in ovarian venous blood and follicular fluid in the rabbit increase significantly following mating or i.v. injection of LH. To study the dynamic changes occurring in these compartments and to determine whether more steroids are secreted directly into ovarian venous blood or into follicular fluid following gonadotrophin stimulation, ovarian venous blood and follicular fluid were measured simultaneously in rabbits before and at 5, 10, 30 mm and 1, 2, 3#{189}, 5, and 9 h after an i.v. injection of an ovulatory dose of LU (NIH-S18, 50 pg/rabbit). Ovarian venous output of progesterone (P4), testosterone (T), and estrogen (E) was significantly elevated (P<O.05) by 5 mm after LH. E and T remained el(cid:1),vated for 2 h, after which time they started to decrease, returning to basal levels at 5 h. At 9 h, output of E and T was significantly (P<0.05) less than basal levels. In contrast, P4 remained elevated for 5 h followed by a significant decrease (P<0.05) at 9 h. However, these levels were 500% greater than basal levels. The average overall increases in ovarian output for P4 and T were approximately 1000% whereas that of E was 2 50%. The changes in steroid concentrations in follicular fluid were less dramatic. Significant increases (P<0.05) were observed 10 mm after LH injection for P4, T, and E. These concentrations were maintained 2 and 3#{189}h for T and E and 5 h for P4. After 3#{189}h (T and E) or 5 h (P4) steroid concentrations decreased to basal levels (P4 and E) or levels significantly less than basal levels (T). For all 3 steroids, an approximate 200% elevation in the steroid concentration of follicular fluid was observed. These results suggest that the majority of the newly synthesized steroids is secreted directly into the ovarian vein while small amounts are secreted into the follicular fluid. Furthermore, the fact that the follicular fluid steroid concentrations show minor increases following gonadotrophmn stimulation may suggest that they contribute minimally to the significant increase in steroid output by the rabbit ovary.