Effects of fungal toxins on renal slice calcium balance

Citrinin and ochratoxin A disrupt renal function in many animal species. The mechanism(s) underlying these actions is (are) unclear. Although citrinin has been shown to bind covalently to renal tissue, there also is evidence that it is active in the unmetabolized form. Altered calcium homeostasis has been suggested as an event which might mediate cell injury and/or death; a possible role for calcium in citrinin- or ochratoxin A-induced nephrotoxicity is reported here. Renal cortical slice calcium balance was monitored by the uptake of 45Ca. Either ochratoxin A or citrinin added to fresh renal cortex slices enhanced 45Ca accumulation. These effects were evident as early as 5 min after addition of the toxins. Greater 45Ca uptake occurred with bathing solution calcium concentration of 1.1 mM than in the absence of added carrier calcium. Finally, the effect of citrinin to reduce p-aminohippurate accumulation by renal cortical slices was greater in the presence of calcium than in its absence.