Pre-ovulatory elevation of rat ovarian prostaglandins F, and its blockade by indomethacin.

Prostaglandins of the F series have been measured, by radioimmunoassay, in ovaries of prepubertal rats in which first estrus was synchronized by injection of pregnant mare serum gonadotropin. Marked elevations, up to 20-fold, were observed approximately in parallel with the endogenous luteinizing hormone surge which occurs on the evening of proestrus, and within 4 h after injection of exogenous luteinizing hormone on the morning of proestrus. Injection of indomethacin, 0.8 mg per rat, at 14:45 on proestrus, prevented the increase in ovarian prostaglandins F without significantly reducing the proestrous elevation of serum luteinizing hormone. These observations support elevation of serum luteinizing hormone. These observations support a physiologic role of prostaglandins F in rat ovarian responses to luteinizing hormone.