The metabolic fate of the synthetic prostaglandin cloprostenol ('Estrumate') in the cow: use of ion cluster techniques to facilitate metabolite identification.

The metabolic fate of the synthetic prostaglandin cloprostenol ('Estrumate') in the cow has been studied. Following intramuscular administration of 0.5 mg and 10 mg of [14C]cloprostenol to cows urinary excretion accounted for 58.2% and 56.3% of the dose respectively. Unchanged cloprostenol and its tetranor acid, probably formed by beta-oxidation, were the major components identified in urine. The tetranor acid was also present as a glucuronide conjugate. This synthetic prostaglandin analogue is apparently a poor substrate for the enzymes 15-hydroxyprostaglandin dehydrogenase and 13,14-reductase, which are responsible for the rapid metabolic deactivation of endogenous prostaglandins, as no components identified in urine were found to have undergone metabolic attack at the C-15 atom in the cloprostenol molecule.