MYCOTOXINS AND THE AVIAN KIDNEY - ASSESSMENT OF PHYSIOLOGICAL-FUNCTION

The avian kidney has shown a remarkable ability to maintain adequate a nd even normal function in the face of a mycotoxin challenge. Full eva luation of the nephrotoxicity of a substance must therefore go beyond pathological and ultrastructural documentation and include a complete functional evaluation. To date, only three nephrogenic mycotoxins, cit rinin, ochratoxin A, and aflatoxin B-1 have been assessed for their ab ility to alter avian renal function. At non-lethal doses, citrinin app ears to have acute reversible effects on the distal portion of the nep hron, possibly acting to inhibit water absorption. Ochratoxin A is mor e potent and less acute than citrinin,but less site-specific in that b oth proximal and distal tubules are damaged, resulting in severe loss of both fluids and electrolytes. Aflatoxin B-1 at a dosage and duratio n which induced hepatotoxicity, concurrently exerted nephrogenic effec ts such as increased urinary calcium excretion and decreased inorganic phosphate excretion. In commercial broilers aflatoxin B-1 has been sh own to decrease plasma levels of 25-hydroxy vitamin D, 1,25-dihydroxy vitamin D and may also decrease endogenous parathyroid hormone synthes is and the renal sensitivity to parathyroid hormone. Furthermore, expo sure to aflatoxin B-1 may cause prolonged alteration in renal function such as reduced glomerular filtration rate. This review summarizes th e studies which have been conducted to evaluate avian renal function d uring both acute and chronic exposure to these three mycotoxins.