Intracortical distribution of renal blood flow during saline infusion in dogs.

Abstract

AbstractThe increase in sodium excretion induced by isotonic saline infusion has been attributed to a redistribution of blood flow within the cortex to “salt‐loosing” superficial nephrons. To test this hypothesis, mean blood flow to outer (OCF) and inner (ICF) cortex was measured in dogs before and during saline expansion, using H2‐clearance rates as indicator of local blood flow. Mean total blood flow (RBF) was measured with an electromagnetic flowmeter. During infusion of 0.9 % NaCI, 30 ml/min for 30–80 min, urine flow increased from 1.1 to 7.5 ml/min, glomerular filtration rate from 39.8 to 49.1 ml/min, RBF rose from 214 to 276 ml/min, OCF from 3.43 to 3.87 ml/min and ICF from 3.50 to 3.91 ml/min. OCF/ICF did not change significantly during saline expansion. Autoregulation of local blood flow was maintained after saline loading with no change in OCF/ICF within the pressure range of autoregulation. Since massive saline infusion is followed by a parallel increase in blood flow to outer and inner cortex, it is concluded that intracortical redistribution of blood flow is not the mechanism of natriuresis during saline loading.