1. Microsomal prostaglandin synthesis and tissue prostaglandin concentrations in the kidneys of rats made diabetic by pretreatment with alloxan or streptozotocin were significantly decreased but were unchanged in lungs.
2. Prostaglandin inactivation was increased in kidneys of alloxan-diabetic rats but not changed in streptozotocin-diabetic kidneys or in the lungs of either group.
3. These changes in prostaglandin metabolism may cause a renal prostaglandin deficit and could contribute to certain pathological sequelae observed in diabetes mellitus.