Electrolyte and fluid transport in the kidney are regulated in part by arachidonic acid and its metabolites. (±)17-HETE is the racemic version of a cytochrome P450 (CYP450) metabolite of arachidonic acid that has stereospecific effects on sodium transport in the kidney. At a concentration of 2 μM the (S)-enantiomer of 17-HETE inhibits proximal tubule ATPase activity by as much as 70%, whereas the (R)-isomer is inactive.