Circulating mediators of proteinuria in idiopathic minimal lesion nephrotic syndrome

The pathogenesis of proteinuria in idiopathic minimal lesion nephrotic syndrome (IMLNS) remains to be elucidated. The most-accepted hypothesis is that the increased glomerular permeability to plasma proteins results from the effect of circulating factors on glomerular capillaries. This report critically reviews the current studies that have attempted to isolate and characterize this putative factor(s). Products released from hepatocyte or peripheral blood mononuclear cells or isolated by chromatography from serum or plasma have been tested in rats for their role in inducing proteinuria. These factors have been infused into the isolated kidney preparation or into the intact animal as a single venous injection, or continuously by pump for a period of 4 h to 7 days. Several of these isolated factors have been shown to induce proteinuria in rats. However, their exclusive pathogenetic role is questionable since none is always present in all IMLNS patients during relapse. Therefore, the increase in proteinuria in these patients may result from a single or a variety of factors as yet to be identified.