Effects of inhibitors of steroid biosynthesis on prostaglandin formation in rabbit ovarian follicles

Luteal phase variations in endogenous concentrations of prostaglandins PGE and PGF and in the capacity for their in vitro formation in the human corpus luteum

One evidence for a luteolytic role for prostaglandin F2 alpha in the human is the increase in luteal PGF at times corresponding to luteolysis as reported earlier by us and other groups. There have been other contradictory reports on this point. In the present experiments we have measured the concentrations of PGE and PGF in 16 more human corpora lutea and have determined the capacity of those tissues to form PGE and PGF in vitro. PGF concentrations were highest in the mid luteal phase but were accompanied by high PGE concentrations. On the other hand, in the late luteal phase PGF concentrations, lower than in mid luteal but generally higher than in early luteal phase, were significantly higher than PGE concentrations. This pattern in PGE and PGF concentrations was also evident in the capacity of these tissues to form these compounds in vitro. In view of the known capacity of PGE2 to counteract the luteolytic effect of PGF2 alpha, these variations in the relative concentrations of PGE and PGF during the luteal phase may be of significance in the process of luteolysis in the human.

Concentration of prostaglandins PGE and PGF, estrone, estradiol, and progesterone in human corpora lutea

The concentrations of prostaglandins PGE and PGF, estrone, estradiol and progesterone in human corpora lutea were measured by radioimmunoassay at various stages of the luteal phase of the menstrual cycle. The concentrations of PGF were found to be significantly higher in both the mid and late luteal phases than in the early luteal phase. In the mid luteal phase there was a concomittant increase in PGE levels, but these levels had declined in the late luteal phase. Steroid concentrations were generally lower in the late luteal phase. It has been postulated that in the human corpus luteum locally produced prostaglandins may be responsible for luteolysis. Our data on the concentrations of PGF and PGE in corpora lutea at various stages of the luteal phase support such a possibility.