Erythrocyte and albumin distribution in the kidney following warm ischemia. A study in rats.

A dark zone of probably stagnant erythrocytes, localised primarily to the inner stripe of the outer medulla, is always found in acute renal failure caused by clamping of the renal artery for 45 min. To test the possible accumulation of red cells, the regional renal red cell content was investigated with 51Cr labelled red cells injected before, during and 10 min after the recirculation. Analyses were made of the volumes of (1) cells remaining from the period of clamping, (2) cells aggregated 0--10 min after recirculation and (3) cells still circulating 10--20 min after recirculation. In the inner stripe the total red cell volume was 21.8 +/- 2.2 microliter . 100 mg-1 (control value 9.3 +/- 0.6), where 26% remained from the period of clamping, 46% had accumulated 0--10 min after recirculation, and only 28% had entered the region 10--20 min after recirculation. The same pattern of response, though less pronounced, was also found in the inner zone. In the cortex the total red cell volume was 6.3 +/- 1.2 microliter . 100 mg-1 (control value 4.4 +/- 0.3), where 24% remained from the period of clamping, 32% were accumulated and 44% remained circulating. The plasma volume as investigated from 131I-labelled albumin was markedly increased in all zones, probably due to extravasation of the tracer. It is suggested that red cell accumulation plays an important role for the medullary ischemia found in ischemic acute renal failure.