Urinary enzyme excretion and renal lactate dehydrogenase isoenzyme pattern in acute HgCl2 nephropathy of rat

Determination of urinary glutathione S-transferase and lactate dehydrogenase for differentiation between proximal and distal nephron damage

Cytosolic glutathione S-transferase (GST) activity is confined to the proximal convoluted and straight tubules. Damage to these parts of the nephron should result in leakage of GST into the urinary space. Lactate dehydrogenase (LDH), in contrast, is more generally distributed along the nephron. Measurement of both enzyme activities could therefore be expected to discriminate between different localizations of nephrotoxicity. To test this hypothesis, we determined both enzyme activities in 24 h urine samples from 10-12 female Sprague-Dawley rats, each treated with single i.p. injections of puromycin aminonucleoside (PAN, 130 mg/kg), Na2 CrO4 10, 20, 30 mg/kg), mercuric chloride (HgCl2, 0.5, 0.75, 1.0 mg/kg), folic acid (125, 350, 375 mg/kg), ethyleneimine (0.5, 2.0, 5.0 microliters/kg). Bovine serum albumin (BSA) was injected by the same method, twice daily on 3 consecutive days (2.5, 7.14 g/kg). The results obtained indicate a characteristic dose- and time-dependent pattern of excreted enzyme activities for each of the tested compounds. In both models with primarily glomerular damage, proximal tubular parts were also affected, as could be demonstrated by increased urinary GST and histopathological changes. Damage, mainly to the S1/S2 segment by 20 or 30 mg Na2 CrO4/kg, resulted in moderate to marked increases in LDH excretion, while GST was only moderately elevated at 30 mg/kg. Extreme increases in GST and LDH output were measured after predominant S3 segment damage after 0.75 and 1.0 mg HgCl2/kg. The distally active compounds, folic acid and ethyleneimine, did not increase GST excretion at lower doses. At the high doses, a small rise in GST excretion indicated some, probably secondary, proximal tubular involvement, which correlated with the histopathological findings in these groups.

Comparative studies on nephrotoxic effects of tris (2,3-dibromopropyl) phosphate and bis (2,3-dibromopropyl) phosphate on rat urinary metabolites

The mechanism of Tris-BP or Bis-BP (a metabolite of Tris-BP) induced nephrotoxicity was investigated by determining urinary excretion of enzymes and selected metabolites. Rats received single oral doses of 0, 71.7, 143.4 and 286.8 mumol/kg tris (2,3-dibromopropyl) phosphate (Tris-BP) or bis (2,3-dibromopropyl) phosphate (Bis-BP). Urine was collected over a 24 h period and subjected to biochemical examinations. Comparative studies on Tris-BP- and Bis-BP-induced nephrotoxicities were carried out for abnormal patterns of urinary excretion. The urinary excretion of glucose was higher in Bis-BP than Tris-BP at a dose of 143.4 mumol/kg, but this pattern reversed at a dose of 286.8 mumol/kg. Peak lactate excretion occurred later than peak glucose excretion with 143.4 and 286.8 mumol/kg Tris BP and 143.4 mumol/kg Bis-BP. Bis-BP 286.8 mumol/kg caused a transient urinary elevation of lactate on Day 2. Uric acid was excreted at higher levels for Bis-BP than Tris-BP on day 2 of urine collection. Activities of urinary enzymes including alkaline phosphatase, aspartate aminotransferase and gamma-glutamyltransferase, were different on the first day of post-treatment for Tris-BP and Bis-BP. Leucine aminopeptidase and lactate dehydrogenase levels differed on the second day. Activities of the former enzymes on the day 2 urine suggested a transformation of Tris-BP to Bis-BP. Urinary patterns of lactate dehydrogenase isoenzymes (LDH-1-LDH-5) were different between Tris-BP and Bis-BP when rats were treated with the dose of 286.8 mumol/kg: Tris-BP caused a higher excretion of LDH-4 and LDH-5 in urine on day 1 and all five isoenzymes into the day 2 urine. Bis-BP caused slightly higher excretion of LDH-5 and LDH-4 into the day 1 and 3 urine, respectively. Bis-BP but not Tris-BP caused abnormally urinary excretion of sodium ion. Histopathologically, the nephrotoxic effect of Tris-BP appeared one day later and was more obvious than that of Bis-BP in rats after single oral administration.