Changes in urinary enzyme activity and histochemical findings in experimental tubular injury induced by gold sodium thiomalate

To elucidate the renal injury induced by gold treatment, we administered various doses of gold sodium thiomalate (GST) to Wistar rats and investigated alterations in the urinary enzyme activity, gamma-glutamyl transpeptidase (gamma GTP) and N-acetyl-beta-glucosaminidase (NAG) activity, and histochemical change of enzymes, gamma GTP, alkaline phosphatase (ALP) and acid phosphatase (ACP) activity in the renal tissue. The single administration of a large dose of gold salts induced acute tubular necrosis and enzyme leakage was detected histochemically without damage to the glomerulus. After chronic administration of small doses of gold salts, the urinary gamma GTP activities gradually increased, but urinary NAG activities did not. These findings suggested that the change in urinary enzyme activities, which leaked from inside of brushborder or lysosome, indicated the degree or localization of tubular damage, because renal tubules were selectively injured by gold salts.