Urinary excretion of vitamin C in chronic renal failure and after renal transplantation.

Urinary excretion of vitamin C was investigated in 44 patients with chronic renal diseases and in 25 patients after renal transplantation with various mean glomerular filtration rates. In both groups a hyperbolic relationship was observed between FE vitamin C and CCr. In addition, direct relationships were found between FE vitamin C and FE Na, FEK and FE H2O in both groups. Various chronic renal diseases and treatments had no influence on the investigated relationships. In 16 healthy subjects urinary excretion of sodium during maximal water diuresis did not increase but urinary excretion of vitamin C significantly increased. In 10 patients in the polyuric stage of chronic renal failure without dialysis treatment during Giordano-Giovanetti-Maggiora diet with addition of sodium chloride the urinary excretion of sodium increased but that of vitamin C was not influenced. The results obtained for the biochemical parameters tested suggest that the urinary excretion of vitamin C depends on the urinary excretion of water.