Blood flow distribution and tissue solute content of the isolated-perfused kidney

Summary

Isolated renal perfusion experiments were performed in the dog kidney to evaluate solute composition of cortex, medulla, and papilla and intrarenal blood flow distribution after 1 to 4 h of normothermic blood perfusion. Tissue slices were assayed for sodium, potassium, urea and water content and external monitoring of¹³³Xe washout and radionuclide-labelled microphere distribution were utilized to determine intrarenal blood flow distribution. Between the first and fourth hours of renal perfusion, total renal blood flow increased secondary to a decrease in renal vascular resistance and urine osmolality decreased. Concurrently there was a reduction in medullary tonicity primarily due to a loss of both urea and sodium. During this same period of time, there was a redistribution of intrarenal blood flow from outer cortex to inner cortex as determined by the microsphere technique. In addition, the distribution of¹³³Xe was significantly altered: radioactivity of Component I decreased from 82±1% to 62±5% while radioactivity increased in Component II from 9±1% to 19±2%. Dissipation of the hypertonic medullary interstitium and alteration of intrarenal blood flow distribution may explain the observed loss of urinary concentration as well as other functional alterations encountered in the isolated perfused kidney.