Prostaglandin Falpha, progesterone and oestrogens in relation to parturition in sheep

Six hourly blood samples were collected from either the uterine vein or posterior vena cava of 8 conscious ewes over a period of about 1 week prior to and 2 days after parturition. In addition blood was also collected simultaneously from the jugular vein. Using sensitive radioimmunoassay techniques, these samples were analyzed for PGF2 alpha, progesterone and oestrogens. The results indicate that concentrations of PGF2 alpha in sheep blood started to rise before a fall in progesterone concentrations. A rise in total oestrogens also preceded the fall in progesterone concentrations. It was however not possible to show a temporal relationship between the rises in oesterogens and PGF2 alpha concentrations.