The renal removal of injected [14C] histamine from the blood in dogs.

The amounts of [(14)C]histamine in arterial blood, in renal venous blood and in urine during a steady intravenous infusion of [(14)C]histamine were measured in five anaesthetized dogs. The extraction ratio for [(14)C]histamine was 0.7 to 0.8, indicating that the histamine was efficiently taken up from the blood by the kidney. Only a small part (14 to 18%) of the [(14)C]histamine removed from the blood by the kidney appeared in the urine as histamine. Evidence was obtained that [(14)C]histamine was metabolized in the kidney not only by histaminase (diamine oxidase) but also by the histamine methylating enzyme.