Effects of thiabendazole (TBZ) on mitochondrial function in renal cortex of ICR mice

Abstract

The effects of thiabendazole (TBZ) on mitochondrial function of the renal cortex were investigated in ICR mice. Mice were given 1000 or 2000 mg TBZ/kg body weight by gavage and mitochondria were isolated from the renal cortex for the measurement of respiratory rates. The state 3 and DNP-uncoupled respiratory rates of renal cortical mitochondria were dose-dependently depressed at 6 hours after dosing. The depression of these respiratory rates of renal cortical mitochondria was more marked at 16 hours after dosing. There was no depression in these respiratory rates of renal cortical mitochondria at 3 hours after dosing, although renal cortical concentrations of TBZ were higher than those at 6 or 16 hours after dosing. Histochemical examination revealed that NAD-linked isocitrate dehydrogenase, a marker enzyme of mitochondria, was inhibited in renal cortical tubules at 16 hours after dosing of 1000 or 2000 mg TBZ/kg body weight. Furthermore, renal cortical ATP level was significantly decreased at 16 hours after dosing of 1000 or 2000 mg TBZ/kg body weight. The results indicate that administration of TBZ caused mitochondrial dysfunction in renal cortical tubules of mice.

Introduction

Thiabendazole [2-(4′-thiazolyl)benzimidazole; TBZ] has broad anthelmintic activity and is effective in the treatment of various nematode infections in human and animals. It is also widely used as a fungicide in agriculture and the domestic environment.

Toxic effects of TBZ have been found in humans and animals. Intrahepatic cholestasis and haemat-uria or dark urine were reported in man after a course of thiabendazole therapy for parasitic infection (Davidson et al., 1988; Golden et al., 1974; Manivel et al., 1987; Pawlowski and Skrzypinska, 1972; Rex et al., 1983; Roy et al., 1989). Slight anaemia was observed in dogs given TBZ for 2 yr (Robinson et al., 1965) or rats given TBZ for 13 wk (Mikuriya et al., 1981). Subchronic (13 wk) administration of TBZ in the diet caused slight anaemia and liver or kidney injury in mice (Tada et al., 1996). TBZ induced reduction deformity of limbs in mice by oral administration on days 9 to 12 of gestation (Ogata et al., 1984). The incidence of urinary bladder tumours induced in rats by sodium o-phenyl-phenate (OPP-Na) was increased by the simultaneous administration of TBZ (Fujii et al., 1986).

We have investigated the effects of TBZ on the kidneys of mice. Single oral administration of TBZ caused polyuria, glucosuria, proteinuria (Tada et al., 1989), and significant increase of kidney weight and inhibition of organic ion uptake in renal slices (Tada et al., 1992). Using inducers (phenobarbital, β-naphthoflavone or 3-methylcholanthrene) or inhibitors (SKF-525A or piperonyl butoxide) of microsomal monooxygenase system, it was revealed that TBZ-induced renal tubular injury was correlated with blood levels of TBZ, not its metabolites (5-hydroxy TBZ or 2-acetylbenzimidazole) (Tada et al., 1992). This indicates that TBZ-induced renal injury may be attributed to the parent compound rather than its metabolites.

In our previous study (Tada et al., 1994), renal tubular necrosis, which may ultimately lead to death in mice, was first observed at 24 hours after dosing and was more numerous and extensive at 2 or 3 days after dosing. Also, serum urea nitrogen concentration, an indicator of renal function, was significantly elevated at 1 to 3 days after TBZ dosing (Tada et al., 1994). The studies on absorption, distribution and excretion of TBZ in mice revealed that the level of ¹⁴C-TBZ in plasma reached a maximum within 0.5 hr after dosing and then declined rapidly (Yoneyama et al., 1984). Tada et al. (1992)reported that TBZ in blood was not detected in mice at 24 hr after dosing. Thus, renal tubular necrosis and renal dysfunction developed after decline of TBZ concentration in blood. The biochemical responses in renal tubular cells within 24 hr after TBZ dosing seems to be important for understanding the mechanism for renal tubular necrosis. We have studied the structural alterations of mitochondria in renal proximal tubular cells at 24 hr after TBZ dosing (Tada et al., 1994). Mitochondria play an important role in production of energy to maintain cellular integrity. The purpose of the present study was to investigate the time course and dose–response relationships of toxicity and mitochondrial function in the early stages of TBZ nephrotoxicity.