Possible mechanism of unconjugated bilirubin toxicity on renal tissue.

1. The effects of unconjugated bilirubin on rat renal tissue metabolism and organic anion transport were investigated using cortical slices. 2. Unconjugated bilirubin in the medium decreased slice-to-medium ratio of p-aminohippurate, altered intracellular Na+ and K+, and decreased ATP content without modifications of (Na+-K+) ATPase. 3. The effects were similar to those of ethacrynic acid and cyanide but less marked. 4. The presence of probenecid blocked the effect of pigment on intracellular electrolytes. 5. The results suggest that pigment is taken up by renal tissue using the organic anion transport system, and within the cell inhibits ATP production.