On the Metabolism of Prostaglandins E1 and E2 in the Guinea Pig

5/3,7a-Dihydroxy-11-ketotetranor-prostanoic acid was the major metabolite excreted in the urine of guinea pigs injected with tritium-labeled prostaglandin E1, prostaglandin EP, 110~ ,15~-dihydroxy-9-ketoprost-5-enoic acid, lla-hydroxy-9,15-diketoprostanoic acid, and 11~hydroxy-9,15diketoprost-5-enoic acid.A method was developed for quantitative determination of 5p ,'7cr-dihydroxy-l l -ketotetranor-prostanoic acid in 24hour samples of guinea pig urine.The basal excretion of the metabolite in 10 male guinea pigs was 1.34 to 2.74 fig per kg of body weight x 24 hours.Administration of 50 mg of indomethacin per day inhibited the excretion of the urinary metabolite by about 98 %.