Biosynthesis of prostaglandin F2alpha from arachidonic acid and prostaglandin endoperoxides in the uterus.

Formation of prostaglandin F2Alpha in the cow and guinea pig uterus microsomes was studied using 14C-labeled arachidonic acid and prostaglandin H2. The total conversion of arachidonic acid was of a low order and underwent fluctuations during the estrous cycle of the guinea pig, being highest towards the end of the cycle. Injections of beta-estradiol-3-benzoate also resulted in higher activity of the uterine prostaglandin synthetase. The uterine prostaglandin synthesizing system appeared to differ in several respects from that present in seminal vesicles, with regard to the proportions of the products formed and the effects of various agents, e.g. reduced glutathione. An inhibiting factor which supressed the fatty acid cyclo-oxygenase was found to be present in uterine preparations. Prostaglandin endoperoxide (prostaglandin H2) was very efficiently reduced to prostaglandin F2alpha by cow and guinea-pig uterus microsomes. Prostaglandin G2 also gave rise to prostaglandin F2alpha. Prostaglandin E2, on the other hand, was not reduced. Both the inhibiting factor and the endoperoxide reducing activity are likely to be parts of a highly specialized mechanism that modulates prostaglandin F2alpha formation in the uterus.