Renal functions in hens fed graded dietary levels of ochratoxin A.

Renal functions: Glomerular filtration rate (inulin clearance), tubular excretion rate of PAH (p-aminohippurate), and concentrating ability (osmotic urine to plasma ratio after injection of vasopressin) were measured in hydrated, conscious hens. The purpose of the investigation was to measure the effects of ochratoxin A, a nephrotoxic secondary metabolite of fungi. Four experimental groups were examined. A control group, two groups with exposure for 49 weeks to a low and a high level of contamination, and a third group exposed at the high level for 2 weeks. The average GFR was reduced by 12% in the first group, by 28% in the second, and by 8% in the third group. Similar reductions were found in the total plasma protein concentration by 14%, 17%, and 2% respectively. The renal concentrating ability in the three groups was reduced by approximately 15%. The tubular excretion of PAH was not reduced at low plasma concentrations, but reduced by 1/2 at higher concentrations. In control birds the excretion of PAH followed Michaelis-Menten kinetics. The apparent “Km” was 53.2 mg/100 ml, the Tmax 20.4 mg/kg min. The ultrafiltrable fraction of plasma PAH was 0.86. The renal changes are in accordance with morphological changes reported elsewhere, and show that the levels of ochratoxin A used in this study are significantly nephrotoxic.