The role of the blood in metabolism of prostaglandin E1 in the cat lung.

We found that when 15-keto-PGE1 was added to cat blood, it was converted to 13, 14-dihydro-15-keto-PGE1 (dihydro-keto-PGE1) by a NADH-dependent enzyme associated with some formed element(s) in the blood. When PGE1 was injected into the pulmonary artery of blood-perfused lungs, the only metabolite detectable in the pulmonary venous blood was the dihydro-keto-PGE1. However, when the lungs were perfused with an artificial perfusate containing no blood cells, a small amount of 15-keto-PGE1 was detected in the venous effluent. Therefore it would appear that a blood-borne delta13 reductase was partially responsible for the conversion of PGE1 to dihydro-keto-PGE1 on passage through blood-perfused cat lungs.