A Comparison of the β-Glycosidase Excretion during Kidney Damage Induced by 4-Nitrophenylarsonic Acid and by Rabbit Anti-Rat Kidney Antibodies

Abstract. In a study of the value of urinary enzyme activities as an indication of glomerular or tubular damage, the effects of two nephrotoxic agents (4-nitrophenylarsonic acid and rabbit anti-rat kidney serum) on the urinary excretion of four β-glycosidases were compared using fluorimetric assays with 4-methylumbelliferyl substrates. The electrophoretic mobilities on starch gel of urinary β-galactosidase, β-glucosidase, β-glucosaminidase and β-glucuronidase, at various times up to 26 days after the injection of the nephrotoxins into the rat, were compared with those of the corresponding enzymes present in normal rat urine, kidney and serum. 4-Nitrophenylarsonic acid causes tubular damage characterised by an immediate rise in the rates of excretion of the four β-glycosidases, followed by a return to normal values. In Masugi glomerulonephritis the immediate rise in enzyme excretion is much less marked but greater increases occur after 10 to 12 days. The increases in excretion rate correlate roughly with the stages of the disease. Both glomerular and tubular damage produce characteristic changes in the excretion of all of the enzymes studied, but β-glucosidase appears to be the most useful indicator of kidney tubular damage, as it is the least widely distributed of these enzymes and is not normally found in urine or serum at significant levels of activity.