Effects of Histaminase Inhibitors on the Blood Pressure Responses in Dogs to Histamine Injected into the Renal Artery.

Summary. 1. The effects on the dog's blood pressure of histamine injected by vein or into the femoral or renal artery have been studied. 2. The effects of two histamine analogues, which were not oxidized by histaminase in vitro were also studied under the same conditions. 3. As judged from the relative effectiveness of histamine injected by these routes the kidney had a considerable capacity to remove injected histamine from the circulating blood. 4. Histaminase‐resistant histamine analogues were not removed as effectively as histamine by the kidney. 5. Histaminase inhibitors, such as aminoguanidine, B 1 ‐pyrimidine and isonicotinylhydrazine potentiated the depressor responses to histamine given into the renal artery but not those to histamine given into the femoral artery or by vein. 6. The depressor responses to the histaminase‐resistant histamine analogues were not potentiated by the inhibitors.