Role of renal uptake of plasma protein in compensatory renal hypertrophy

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Abstract
Renal handling of endogenous plasma ribonuclease was studied in an attempt to relate compensatory renal hypertrophy to altered renal clearance of plasma protein. Ribonuclease activity in plasma and in remaining [rat] kidney increases after unilateral nephrectomy. The significant arterial-venous difference in enzyme activity across the kidney and the identical biochemical characteristics (pH optimum, substrate specificity) of renal and plasma enzyme indicate that the renal enzyme arises from the plasma. Localization of the renal enzyme to membrane-bound, subcellular particulates of the cortex is consistent with renal uptake of the enzyme by endocytosis from the glomerular filtrate. Increased renal uptake of filterable protein is capable of stimulating renal DNA synthesis; renal sequestration of parenterally administered egg white lysozyme (mol wt 17,500) is associated with enhanced incorporation of p32 into renal DNA. It is proposed that elevated plasma concentrations of ribonuclease and other low molecular weight proteins result from reduction of renal mass, and that increased uptake of these proteins by the remaining kidney is a stimulus for initiating compensatory renal hypertrophy.