Evidence that the pituitary gland is the site of inhibitory action of porcine follicular fluid upon FSH secretion in the rat.

This study has examined the effects of porcine follicular fluid (PFF) on the adenohypophyseal secretion of LH and FSH following LHRH treatment. The animal model selected for study the the proestrous rat in which preovulatory LH and FSH surges were blocked with phenobarbital. To elicit the release of gonadotropins from this preparation, two different i.v. LHRH infusion protocols were used. The first elicited a proestrous-like LH and FSH surge while the second infusion schedule evoked the predominant release of FSH with only minor changes in LH. PFF suppressed LHRH-induced FSH secretion in both preparations but had only negligible effects on LH secretion. Interestingly, the suppressive effects of PFF were variable and depended upon the mode in which LHRH was presented.