Prostaglandin levels in peripheral plasma during the reproductive cycle

The levels of the major plasma metabolite of PGF2alpha, 15-keto-13,14-dihydro-PGF2alpha, were followed in peripheral venous plasma during the reproductive cycle in three species, viz., the ovine, bovine, and human species. In the sheep and cattle low levels were encountered during the major part of the estrous cycle. During the last days of the cycle high levels of the prostaglandin metabolite were found, coinciding with the decrease in progesterone production. The human menstrual cycle was characterized with respect to some plasma steroids and peptide hormones. The prostaglandin metabolite levels were low throughout the cycle, generally ranging between 30 and 70 pg/ml. No significant variation in the prostaglandin production could be seen during the menstrual cycle.