Evidence for the presence of a K-dependent acidifying adenosine triphosphatase in the rabbit renal medulla.
To date direct evidence for the presence of a H-K-ATPase in the medulla comes from proton and potassium transport studies performed on K-restricted animals and K dependent ATP hydrolysis and Rb uptake in both normal and K-depleted animals. The present work examines K-dependent acidification in the medulla of rabbits on normal K diets. A membrane vesicle preparation was developed that was enriched for apical membranes derived from the renal medulla. Adenosine triphosphate (ATP)-dependent vesicular acidification was present and the extent of vesicular acidification was dependent on ambient K concentration. Moreover, ATP hydrolysis was dependent on ambient K concentration. K-dependent acidification was inhibited by the specific inhibitor of the gastric H-K-ATPase, SCH28080. However, significant acidification was observed in the absence of K that was not inhibited by SCH28080. The data suggest that an H-K-ATPase similar to the gastric H-K-ATPase is present in the renal medulla of rabbits on a normal K diet. The component of acidification and ATP hydrolysis that is independent of K concentration likely represents the previously characterized vacuolar H-ATPase.
Curran
K A
KA
Division of Nephrology, Hypertension and Transplantation, University of Florida, Gainesville.
Hebert
M J
MJ
Cain
B D
BD
Wingo
C S
CS
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D005260:Female; D017506:H(+)-K(+)-Exchanging ATPase / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007093:Imidazoles / Q000494:pharmacology; D007679:Kidney Medulla / Q000201:enzymology* / Q000648:ultrastructure; D008861:Microsomes / Q000201:enzymology; D054328:Proton Pump Inhibitors; D011817:Rabbits; D013347:Subcellular Fractions / Q000201:enzymology; D014638:Vanadates / Q000494:pharmacology
D007093:Imidazoles; D054328:Proton Pump Inhibitors; C035235:Sch 28080; D014638:Vanadates; D000255:Adenosine Triphosphate; D017506:H(+)-K(+)-Exchanging ATPase