Objectives: 

In a previous study, we have demonstrated that cisplatin injection, an animal model of tubular damage, evokes an early augmentation of aminopeptidase activities in urine. In this work, we study if the high urinary excretion of these brush-border enzymes in cisplatin-treated rats is accompanied with alterations in renal or plasmatic aminopeptidase activities.

Materials: 

16 Wistar rats were distributed in two groups: Control and CisPt (n=8 each group). Control group received a s.c. injection of 2 ml/kg of saline, and CisPt 7 group was injected with saline containing 7 mg/kg of cisplatin. Rats were housed in metabolic cages and urine samples were collected at 24 hours after treatment. After anesthesia with equitensin, blood samples were obtained by intraventricular punction, and kidneys were dissected. Ala-, Glu-, Cys- and Asp-aminopeptidase activities were determined in urine, plasma and kidney by a fluorimetric kinetic method. We used t test for statistical comparisons, and Welch modification of t test when variances were different.

Results: 

All aminopeptidase activities were significatively increased in urine samples of cisplatin-treated rats versus control group (p<0.05). No statistical differences were found in the plasmatic activity of these enzymes. Cisplatin reduced the activity of these four enzymes in renal tissues. GluAp activity diminished from 37.0 ± 2.35 to 24.9 ± 1.82**, AlaAp from 63.0 ± 3.28 to 38.7 ± 3.64***, CysAp from 46.5 ± 2.60 to 25.2 ± 2.78*** and AspAp from 5.21 ± 0.44 to 3.48 ± 0.40* nmol/min.mg of protein. *p<0.05, **p<0.01, ***p<0.001 versus control group.

Conclusions: 

Cisplatin treatment decreases renal aminopeptidasic activities, probably promoting the release of these brush-border enzymes to the ultrafiltrate, and explaining the early increase in urinary aminopeptidase excretion observed in this animal model of tubular damage. Cisplatin did not modify plasmatic aminopeptidase activities, discarding an extrarrenal origin of these proteins.