The effects of phloretin and carbonyl-cyanide-m-chlorophenylhydrazone (CCCP), both inhibitors of oxidative phosphorylation, on renal urea excretion in Wistar rats were investigated. Phloretin and CCCP infusions did not influence plasma urea concentration (P(urea)), compared with controls (0.15 M NaCl and Tris solution in 0.15 M NaCl-a solvent for phloretin and CCCP). The fractional urea excretion (FEurea) was not altered by phloretin infusion. It decreased significantly only when compared with 0.15 M NaCl infusion (P < 0.05). CCCP infusion had no effect on FEurea. The total amount of urea excreted by urine (UureaV) was not altered by phloretin compared with controls. CCCP significantly enhanced Uurea V only when compared with 0.15 M NaCl (P < 0.001), not when compared with Tris. Glomerular Filtration rate (GFR) increased significantly during phloretin infusion (P < 0.001), CCCP (P < 0.001) and also after Tris in 0.15 M NaCl (P < 0.001), in comparison with 0.15 M NaCl alone. Our results showed that phloretin and CCCP had no effect on urea excretion in rats. The increase in GFR is attributed to Tris, not to phloretin or CCCP. It is concluded that inhibition of oxidative phosphorylation in kidney has no effect on urea excretion.

Institute of Animal Physiology Slovak Academy of Sciences Kosice Czechoslovakia