Studies on the mechanism of renal tubular protein reabsorption.

Amino acids and derivatives were injected intravenously in normal man and the effect on the urinary excretion of albumin, free light chains and beta-2-microglobulin determined. From the results we hypothesise that the initial event in normal protein reabsorption is binding between a free positive amino- or guanidino-group of the protein molecule and a negative site on the tubular cell surface. This initial event in the reabsorption process is impeded by molecules containing similar charged groups (arginine, ornithine, lysine, EACA and Cyclocaprone). Using high doses of lysine, complete or near-complete inhibition of tubular protein reabsorption is obtained. The glomerular filtration rate in preliminary experiments is found to be of the order of 300 microgram/min for albumin.