Distribution of capillary blood flow in rat kidney during postischemic renal failure

Changes in distribution of intrarenal blood flow were studied in anesthetized rats during the acute phase of postischemic renal failure (1 h renal artery occlusion, 1 h reflow). Distribution of capillary plasma flow was determined by injecting fluorescein-isothiocyanate-globulin and lissamine-rhodamine-B200-globulin 1, 3, or 10 min prior to rapid freezing of the kidney. In histological sections it was possible to differentiate among the vessels perfused during the time of labeling because of their respective fluorescence. In these experiments all glomeruli became labeled within 1 min, although in contrast to the controls, the glomerular capillary network itself was not filled completely in the postocclusion organs. Incomplete labeling was far more pronounced, however, in the postglomerular network of the occlusion experiments. Due to this effect in the cortex and in the medulla, 11 and 58% of tissue, respectively, were found lying at a distance of more than 60 microns from the next vessel labeled after 1 min of dye circulation. In the control experiments there was no tissue within this distance. Prolonging the time of labeling up to 10 min caused little change in this pattern of distribution. In the occlusion experiments, the globulins were observed in nearly all Bowman spaces, but in less than half of the tubular lumina. The results strengthen the view that the ischemic insult leads primarily to disturbance of the postglomerular perfusion, which then results in trophic damage of the tubular system mainly within the renal medulla.