A study in the maintenance phase of ischaemic acute renal failure in the rat.

The fate of the trapped deformed erythrocytes seen in the early recirculation phase after ischaemia and the generation of long Tamm-Horsfall (TH) cylinders in the renal medulla during the first week after recirculation was studied in rats. In an in-vitro study the effects of different concentrations of TH protein on the permeability to Na+ of a semipermeable membrane were also investigated. The trapping of erythrocytes was found to be a reflow phenomenon, as there was no increase in the capillary area of the medulla in kidneys subjected to ischaemia but with no recirculation. This area increased to a maximum of 34.6 +/- 2.07% 20 min after recirculation and decreased to a normal value of 3.3 +/- 0.74% 1 day after the primary ischaemia. The area occupied by cylinders increased to a maximum of 19.2 +/- 1.4% 2 days after the primary damage and was as large as 16.7 +/- 1.47% after 1 week. It was also shown that the diffusion half-time of Na+ ions across a semipermeable membrane increased from 11.4 +/- 0.45 min to a maximum of 32.2 +/- 2.19 min with a protein concentration of 1 mg ml-1. It was concluded that the trapping of erythrocytes alone could not explain the decrease in renal function 1 week after the primary damage, but that the blockade of the tubules by the long homogeneous TH cylinders could be responsible for this decrease.