Pre and post ovulatory changes in the concentration of prostaglandins in rat Graafian follicles

The concentrations of prostaglandin F (PGF) and prostaglandin E (PGE) were measured by radioimmunoassay in isolated GRaafian follicles of mature female rats during the pre and post ovulatory period of the estrous cycle. The levels of these prostaglandins were low and relatively constant from 8 a.m. to 4 p.m. on the day of proestrus, but there was a marked increase at 8 p.m. of proestrus reaching an apparent maximum at midnight (PGF 18 fold, PGE 70 fold). By 4 a.m. to 8 a.m. on the morning of estrus these prostaglandins declined rapidly to levels similar to those observed between 8 a.m. and 4 p.m. on the day of proestrus. The increases in prostaglandin levels occurred after the LH peak and apparently before the time of ovulation. These data confirm the role of PGF and PGE in the local mechanism of ovulation in the normal adult of a spontaneously ovulating animal species.