Effects of ovine follicular fluid on plasma LH and FSH secretion in ovariectomized ewes to indicate the site of action of inhibin.
Ovariectomized ewes were given 2 ml s.c. injections of ovine follicular fluid (oFF) (N = 3) or serum (N = 3) and blood samples were collected each day for 3 days. Follicular fluid caused a significant (P less than 0.005) reduction in FSH within 1 day, but did not affect mean LH values. Two groups of 3 ewes were treated as above but sampled intensively (each 10 min for 6 h) on Days 1 (before treatment) and 4; mean plasma FSH concentration and plasma LH pulse frequency and amplitude were ascertained. Significant (P less than 0.005) reduction of FSH concentration was seen in the oFF-treated ewes. A non-specific reduction in LH pulse amplitude, but not pulse frequency, was noted in the control ewes. This experiment was repeated with 2 groups of 4 ewes that were conditioned to the experimental environment and effects on LH secretion were not observed in the controls given serum. Treatment with oFF caused a 70% reduction (P less than 0.005) in plasma FSH and a small (30%) but significant (P less than 0.005) reduction in mean LH concentrations. The latter was probably associated with a reduction in LH pulse amplitude in 3/4 animals (N.S.) with no change in LH pulse frequency. Treatment with oFF, as in Exp. 1, caused a 95% reduction in FSH values and significant (P less than 0.01) reduction (32%) of LH pulse amplitude in ovariectomized ewes that had been subjected to hypothalamo-pituitary disconnection and in which gonadotrophin secretion was reinstated with pulses of 250 ng GnRH every 2 h. These results suggest that proteins from the sheep follicular fluid, including inhibin, act at the pituitary level to inhibit FSH secretion and may have some effects on LH pulse amplitude.
D000818:Animals; D001826:Body Fluids / Q000378:metabolism*; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood / Q000378:metabolism*; D007265:Inhibins / Q000502:physiology*; D007986:Luteinizing Hormone / Q000097:blood / Q000378:metabolism*; D006080:Ovarian Follicle / Q000378:metabolism*; D010052:Ovariectomy; D010902:Pituitary Gland / Q000378:metabolism*; D012636:Secretory Rate; D012756:Sheep
D007265:Inhibins; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone