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The persistency of fibrin deposits in the kidney during renal diseases could reflect either a defective release of plasminogen activators (PA) or a local excess of PAI. In order to investigate this question, we studied human renal biopsies by immunofluorescence technique with specific antibodies for fibrin, tissue-type plasminogen activator (t-PA), urokinase (u-PA), PAI-1 and PAI-2. By this technique t-PA could be detected in the glomerular flocculus and the endothelium of small arteries of the normal control kidneys. We failed to detect significant fluorescence with other antibodies in normal kidneys. Conversely, in cases of vascular nephropathy with thrombosis the positive fluorescence obtained with anti-fibrin antibodies at the site of thrombosis was associated with a positive fluorescence with anti-PAI-1 and to a lesser extent with anti-t-PA antibodies. u-PA and PAI-2 were not detected in these lesions. Similarly in the most severe forms of crescentic glomerulonephritis, extracapillary fibrin deposits were associated with PAI-1. In one case u-PA was also detected. This is in agreement with our previous findings that glomerular epithelial cells release both PAI-1 and the inactive form of u-PA (pro u-PA). Thus, our results support the hypothesis that PAI-1, which is able to inhibit both t-PA and u-PA, may play a major role in the persistency of fibrin deposits in the human kidneys during pathological conditions.

In twelve patients with acute renal failure, mean plasma levels of atrial natriuretic factor (ANF) and of its second messenger cGMP were found elevated at the early phase of the disease, but tended to return towards normal values at recovery. Variations of plasma ANF and cGMP were correlated significantly (p less than 0.05) with those of total blood volume. At the early phase of the disease, plasma ANF was also correlated with the excreted fraction of filtered sodium (FENa) (r = 0.95). Moreover, plasma ANF and FENa peaked concomitantly at the onset of the diuretic phase in the five patients who were not treated by diuretics or dialysis and were studied sequentially during the course of the disease. It is suggested that enhanced plasma ANF levels might reflect one of the mechanisms of adaptation controlling body fluid balance in acute renal failure.

Four patients with thrombotic microangiopathy had evidence of intravascular C3 activation on presentation which persisted after bilateral nephrectomy. In several serum samples, C3-splitting activity was not associated with the presence of circulating immune complexes, which were detected in all four patients before nephrectomy and in three after nephrectomy.