Postocclusive reactive hyperemia in the rabbit kidney.

HONDA, NISHIO, CHXKARA AIZAWA, AND YAWARA YOSHITOSHL Postocclusiue reactive hyferemia in the rabbit kidney. Am. J. Phvsiol. 215(l): 190-196. 1968.-Postocclusive hyperemia wa$ studied in the intact rabbit kidney. Characteristically, two phases of hyperemia were revealed after release of thp: arterial occlusion: an initial phase of overshoot of flow and a succeeding decrement below the preocclusion level, and a second phase of gradual flow increase. The duration of the initial phase averaged 8 set following a I-min occlusion and increased with longer occlusion periods. The initial overshoot was not demonstrated in the kidney exhibiting control high vascular resistance and in the chronically ureterally obstructed kidney, in which the Bayliss myogenic response appeared to be diminished. The second flow increase was slower in develop ment and more persistent than the initial flow increase. Its magnitude rose with progressively longer occlusions. Venous pressure elevations induced by simple venous occlusion or arterial-venous occlusion suppressed the development of the second flow increase, On the contrary, renal vein pressure elevation produced by infusion of unoxygenated dextran into the renal vein failed to suppress the appearance of the second phase. The findings suggest that myogenic and metabolic factors may both be involved in the mechanisms of reactive hyperemia in the kidney.