Prostaglandin biosynthesis by the rat uterus during the oestrus cycle, temporal correlation with plasma oestradiol and progesterone concentrations, identification of 6 keto PGF 1α as the major metabolite

Abstract

Prostaglandin biosynthesis was studied in the rat uterus during the oestrous cycle. Uterine homogenates were incubated for 20 minutes in the presence of exogenous substrate (2.10 −5M). PGF 2α and PGE 2 were measured by R.I.A.. A sharp peak PGF 2α and a smaller peak of PGE 2 were observed at prooestrus, 20 h. Another small PGE 2 peak occurred at dioestrus II, 15 h. The lowest values of both PGs were found on dioestrus, 15 h. Plasma oestradiol concentration were highest at proestrus, 15 h and 20 h. A sharp progesterone peak occurred at prooestrus, 20 h. The PGF 2α peak is next to the oestradiol peak and is superimposable or lags slightly beyond the progesterone peak. Incubation with 14C arachidonic acid and subsequent analysis of extracts by TLC and scanning showed that the major metabolite is PGI 2, identified as 6 keto PGF 1α. The conversion rate of arachidonic acid into 6 keto PGF 1α is 5 times higher than into PGF 2α. 6 keto PGF 1α was further identified by GC/MS. No significant difference was observed between 6 keto PGF 1α production during oestrus and dioestrus.