A Method for Determining Urinary Enzyme Activities as Nephrotoxic Indicators in Rats

A simple, useful method was developed for detecting drug nephrotoxicity in rats. Rat urine excreted by stimulation of the sacral part of the back was collected in a beaker, and enzymes in 0.2 ml of the urine were partially purified by centrifugal ultrafiltration using an Amicon MPS-1 kit. Activities of N-acetyl-β-D-glucosaminidase (NAG), alanine aminopeptidase (AAP), γ-glutamyltranspeptidase (γGTP) and lactate dehydrogenase (LDH), and the protein concentration of the enzyme preparation suspended in phosphate-buffered saline were represented as creatinine ratios. A marked increase in these enzyme activities and protein concentration were observed in rats with kidneys damaged by treatment with cephaloridine, HgCI2, cisplatin or gentamicin. The patterns of increase of these indicators differed with the drug, but in general, LDH showed the highest response and NAG, the longest lasting one. These data agreed with the results reported by other researchers using dialyzed 24-hr urine. Thus, we concluded that this method is an efficient one for determining drug nephrotoxicity in rats.