The influence of pregnancy on PGF 2α secretion in cattle. II. Urinary levels of 11-ketotetranor PGF metabolites and plasma progesterone concentrations during the oestrous cycle and early pregnancy

Abstract

Radioimmunoassay of the urinary 11-ketotetranor PGF metabolites after i.v. infusion of prostaglandin F 2α (PGF 2α) showed that these metabolites could be detected in the urine in concentrations proportional to the dose of PGF 2α infused. Daily output of the 11-ketotetranor PGF metabolites in the urine was measured in four catheterized heifers during the oestrous cycle and peaks in their excretion were detected at the time of luteolysis, indicated by the decline in plasma progesterone. In five additional catheterized heifers, levels of the metabolites in daily urine samples were determined throughout the oestrous cycle, during early pregnancy following artificial insemination, during cloprostenol-induced abortion, and after embryo transfer. During early pregnancy, there was an absence of the clear peaks of the urinary metabolites seen during luteolysis. However, there was a gradual increase in their concentration starting at about day 20. The results indicate that the measurement of urinary 11-ketotetranor PGF metabolites once or twice daily may serve as a good method for following PGF 2α secretion in long-term studies, especially in regard to changes that take place during pregnancy and embryonic mortality.