Single and multiple doses of ochratoxin A cause apoptosis in kidney tubular epithelium of rat

Ochratoxin A (OTA) is nephrotoxic mycotoxin probably involved in the ethiology of endemic nephropathy. The morphological findings in kidneys of patients with manifest stage of this disease are interstitial, bilateral, non-inflammatory and non-obstructive nephropathy with heavy damage of tubular epithelium and interstitial fibrosis (M. BELICZA and M. VUKELIC in Endemic nephropathy in Croatia, D. Cvoriscec, S. Ceovic and A. Stavljenic-Rukavina Eds, 39-41, Medicinska naklada, Zagreb, 1996). It was found that OTA induces lipid peroxidation, and OTA induced lesions could also be related to oxidative pathways (A.D. RAHIMTULA, J.C. BEREZIAT, V. BUSSACCHINI-GRIOT and H. BARTSCH Biochem. Pharmacol. 37, 4469-4477, 1988). It was found that oxygen reactive toxin metabolites cause apoptosis (M.R. ALISON, C.E. SARRAF Human Experiment Toxicol. 14, 234-247, 1995). This type of cell death does not involve inflammation, and the healing occurs by means of connective tissue formation. The aim of this work was to see whether OTA treatment causes apoptosis in kidney of experimental animals. In experiments adult female Wistar rats were treated with a single or multiple intraperitoneal dose of OTA dissolved in TRIS buffer. Single dose of OTA (1000 mg/kg b.w.) or vehicle only, were given to rats (3 per group), and sacrificed 1, 2, 6 and 9 days afterwards. Kidney sections 4 mm thick, HE-stained, paraffin embedded were prepared. No necrosis was noticed. The number of apoptotic cells was counted in a section of the whole kidney of rat (M. SCHUMER, M.C. COLOMBEL, I.S. SAWCZUK et al., Amer. J. Pathol. 140, 831-838, 1992). The number of apoptotic cells in tubular epithelium (mostly in cortical part of kidney) per kidney section was 19.3 ą 22.8, 12.7ą19.4, 0.3ą0.6 (mean ą SD) and 0 after 1, 2, 6 and 9 days, respectively. Apoptotic cells were not seen in kidney tissue of vehicle treated animals. Multiple doses of OTA (0, 250, 500 and 1000 mg/kg b.w./day/3 times a week for 4 weeks) were given to rats (5-10 per group). In kidney sections of rats killed 2 days after the last treatment with 250, 500 and 1000 mg OTA/kg b.w., 40.0ą13.5, 70.2ą35.3 and 106ą48.9 (meanąSD) apoptotic cells were seen, respectively. No apoptotic cells were seen in kidney sections of control animals treated with vehicle only (N=10). Urine analysis at the end of the treatment with 250 and 500 mg OTA/kg b.w. revealed the decreased concentration of creatinine in urine and increased in serum as compared to controls. Our data showing the connection between OTA and apoptosis support the theory that OTA is involved in the pathogenesis of endemic nephropathy.