valinomycin and Alkalosis

We have shown elsewhere that membranes isolated from the turtle bladder epithelium have both vanadate-resistant (VR) and vanadate-sensitive (VS) components of ATP-dependent H+ transport. VR appears to be due to a vacuolar-type H+ uniport while VS has properties of an H/K exchanger. In the present study we used bladders from chronically alkalotic turtles, which do not acidify urine, and found them to yield membranes which retain VR but lack VS transport. Thus VS occurs only in membranes from bladders secreting acid, implying that VS H+ transport (1) plays a physiological role in the secretion and (2) is a functional marker for the apical membrane of the acid-secreting cells. These results suggest a new model for distal urinary acidification.

Topics: Adenosine Triphosphate; Alkalosis; Animals; Cell Membrane; Epithelium; Hydrogen-Ion Concentration; In Vitro Techniques; Kinetics; Models, Biological; Oligomycins; Ouabain; Turtles; Urinary Bladder; Valinomycin; Vanadates