Effect of histamine and antihistamines on renal hemodynamics and functions in the isolated perfused canine kidney.

Histamine was infused intra-arterially (10-40 mug/min) into isolated blood perfused canine kidneys while functional and hemodynamic parameters were monitored. When perfusion pressure (PP) was kept constant during the infusion of histamine, renal blood flow (RBF) increased from 137 +/- 9 to 181 +/- 9 ml/min (P less than .001). A greater increase in RBF occurred to the inner renal cortex than the outer renal cortex as measured by radioactive microspheres. The fractional outer/inner cortical blood flow changed from 79:21 before histamine to 74:26 during its infusion (P less than .001). Histamine did not alter creatinine clearance (Ccr), urine volume (V), sodium excretion (UNaV) or the fractional excretion of sodium (FENa) or water (FEH20) under these conditions. When renal blood flow was held constant during the infusion of histamine, PP decreased from 126/106 +/- 2 to 100/81 +/- 2 mm Hg (P less than .001). This resulted in a reduction of absolute outer cortical (outer/inner) changed from 77:23 before histamine to 72:28 during its infusion (P less than .001). In contrast to the effects of histamine at constant PP, CCr, V, UNaV, FENa, and FEH20 were decreased when histamine infusion reduced the PP. Administration of the H1 receptor antagonist, diphenhydramine, blocked the hemodynamic effects of histamine whereas the administration of an H2 receptor antagonist, metiamide, did not alter the histamine response. Similar vasodilatory responses to histamine were observed in isolated blood perfused dog and cat kidneys. In contrast, vasoconstrictor responses to histamine occurred in isolated dog and cat kidneys perfused with Krebs' solution and in isolated rabbit kidneys whether perfused with blood or Krebs' solution.