Urinary kidney injury molecule-1 (KIM-1) excretion in rats with experimental cystitis induced by oxazaphosphorines

Oxazaphosphorine agents (cyclophosphamide - CP, ifosfamide - IF) are causative factors of cystitis and also exert a characteristic nephrotoxic effect, clinically manifested by a broad spectrum of disturbances. The aim of the study was to estimate the toxic effect of the abovementioned oxazaphosphorines on the renal tubules by assessment of diuresis and urinary concentration and daily urinary excretion of the kidney injury molecule-1 (KIM-1) in rats with induced and histologically confirmed cystitis.

The study involved 60 rats (equal amounts of ♀ and ♂), including animals treated with CP, administrated four times at the dose 75 mg/kg (group 1; n=10) and treated with IF, administrated four times at the dose 50 mg/kg IF (group 2; n=10) with the suitable control group A (group 3; n = 10), as well as animals receiving either a single dose 150 mg/kg of CP (group 4) or IF (group 5), with an appropriate control group B (group 6).

In both groups 1 and 4, a significant increase in the daily diuresis and decrease of the urinary pH were revealed, compared to the appropriate control group A (group 3) and B (group 6), while IF-treated animals, regardless of the applied doses (groups 2 and 5), were characterized by a urinary pH decrease. KIM-1 urinary concentration in rats from group 1 and 4 was almost three times higher compared to the appropriate control groups A or B, respectively, and the difference was statistically significant. In animals with chronic (group 2) and acute (group 5) ifosfamide- induced cystitis, no statistically significant difference concerning KIM- 1 urinary concentration compared to a control A and B groups was revealed, although a clear tendency of increase of the parameter was observed in the IF-treaded animals. Analysis of daily KIM-1 urinary excretion showed a statistically significant, almost six-fold increase in group 1 and almost two-fold increase in group 2. In the groups with acute model of cystitis, the highest, nearly eight-fold, daily KIM-1 urinary excretion, was revealed in animals treated with single CP dose, compared to the respective control B group, while rats treated with a single IF dose were characterized by a daily urinary KIM -1 excretion, comparable to animals with IF-induced chronic cystitis. The histopathological analysis confirmed cystitis in all animals treated with either CP or IF (groups 1,2,4,5), while no altered kidney microscopic morphology, compared to respective control groups A and B, was observed in those rats.

The study confirmed the proximal tubular dysfunction in rats with both cyclophosphamide- and ifosfamide-induced cystitis, which was reflected by an increased urinary KIM-1 excretion. The disturbance was more emphasized in CP-treated animals, especially in those ones treated with the single, high CP dose. The functional tubulopathy was not accompanied by a structural kidney damage in rats treated with either CP or IF.