Evidence for an acid pH in rat renal inner medulla: paired measurements with liquid ion-exchange microelectrodes on collecting ducts and vasa recta.

We reevaluated the pH in the renal medulla in rats. pH of the vasa recta blood was about 1 pH unit acidic in comparison to the pH of renal artery blood. During furosemide-induced diuresis pH of vasa recta blood increased whereas pH of collecting duct urine further decreased. The acidic pH in the rat renal inner medulla during antidiuresis raises important questions about the source of H+ in inner medulla.