The effects of phloretin and carbonyl-cyanide-m-chlorophenylhydrazone
(CCCP), both inhibitors of oxidative phosphorylation, on renal urea ex
cretion 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 (FE(urea)) was not
altered by phloretin infusion. It decreased significantly only when c
ompared with 0.15 M NaCl infusion (P<0.05). CCCP infusion had no effec
t on FE(urea). The total amount of urea excreted by urine (U(urea)V) w
as not altered by phloretin compared with controls. CCCP significantly
enhanced U(urea) V only when compared with 0.15 M NaCl (P<0.001), not
when compared with Tris. Glomerular Filtration rate (GFR) increased s
ignificantly during phloretin infusion (P<0.001), CCCP (P<0.001) and a
lso after Tris in 0.15 M NaCl (P<0.001), in comparison with 0.15 M NaC
l alone. Our results showed that phloretin and CCCP had no effect on u
rea excretion in rats. The increase in GFR is attributed to Tris, not
to phloretin or CCCP. It is concluded that inhibition of oxidative pho
sphorylation in kidney has no effect on urea excretion.