Reduced intrarenal resistance and autoregulatory capacity after hyperoncotic dextran.

NAVAR, L. G., P. G. BAER, S. L. WALLACE, AND J. K. McI DANIEL. Reduced intrarenal resistance and autoregulatory capacity after hvperoncotic dextran. Am. J. Physiol. 221(l): 329-334. 1971.Renal hemodvnamic and urine flow responses to infusions of hyperoncotic dextran solutions have been studied in anesthetized dogs. Following infusion of 300-500 ml of a 12yh dextran solution, the renal blood flow and intrarenal venous pressure were markedly increased in association with the increased plasma colloid osmotic pressure, but there was no significant change in arterial pressure or glomerular filtration rate. The urine flow, intrarenal resistance, and hematocrit were decreased. Renal blood flow autoregulatory capability was examined in two ways, and it was determined that although intrinsic vascular contractile ability was maintained following the dextran loading, blood flow autoregulation was nearly abolished. Because the differences between control and experimental renal blood flow and intrarenal vascular resistance values at arterial pressures below the autoregulatory range were minimal, the decreases in intrarenal vascular resistance appeared to be restricted to the autoregulating component. An effect on the intrarenal mechanism normally responsible for autoregulation of renal blood flow is postulated. This could be mediated by changes in plasma colloid osmotic pressure, although indirect effects due to dextran leakage into the tubules cannot be discounted.