Clinical localization of tubular transport of exogenous substances exhibiting urine flow dependence excretion.

The proposed method is based on the assumption that a fluid flow dependent tubular transport process in the distal (diluting) segment of the nephron can be influenced by water diuresis as well as osmotic diuresis. If the fluid flow dependent transport process is localized in the proximal part of the nephron only, the urinary excretion of such a substance can be increased by proximal osmotic diuresis but not by water diuresis. By means of this method the localization of fluid flow dependent tubular transport processes of chloramphenicol and its metabolites (arylamines and total nitro compounds) has been studied in 17 healthy volunteers. The results indicate that the flow dependent transport processes of substances under study may be localized in the diluting segment.