Ouabain-insensitive, vanadate-sensitive K(+)-ATPase of rat distal colon is partly similar to gastric H+,K(+)-ATPase.
A membrane fraction from rat distal colon contained both ouabain-sensitive and -insensitive K(+)-ATPase activities, which were measured under Na(+)-free conditions. About 38% of the ouabain-insensitive K(+)-ATPase activity was inhibited by vanadate. It was determined whether the ouabain-insensitive, vanadate-sensitive K(+)-ATPase in the colon is similar or identical to gastric H+,K(+)-ATPase. This colonic K(+)-ATPase activity was inhibited completely by monoclonal antibody HK4001, which inhibits the hog gastric H+,K(+)-ATPase activity but not Na+,K(+)-ATPase or Ca(2+)-ATPase. The colonic ATPase activity was inhibited partly by SCH 28080, which is a specific reversible inhibitor of gastric H+,K(+)-ATPase. The colonic ATPase activity was stimulated by low concentrations of K+ (its half-maximal stimulating concentration was 1 mM) and inhibited by high concentrations of K+ (its half-maximal inhibiting concentration was 10 mM), indicating that high and low K+ affinity sites are present in the colonic enzyme as in gastric H+,K(+)-ATPase and that this enzyme is not fully operative under normal physiological conditions. Two other monoclonal antibodies, which inhibit the gastric H+,K(+)-ATPase activity, did not inhibit the colonic K(+)-ATPase activity. The present results suggest that the colonic ouabain-insensitive K(+)-ATPase is partly similar but not identical to the gastric H+,K(+)-ATPase.
Tabuchi
Y
Y
Faculty of Pharmaceutical Sciences, Toyama Medical and Pharmaceutical University, Japan.
Takeguchi
M
M
Asano
S
S
Takeguchi
N
N
D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000502:physiology; D000818:Animals; D000897:Anti-Ulcer Agents / Q000494:pharmacology; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D001666:Binding Sites, Antibody; D027682:Cation Transport Proteins; D003106:Colon / Q000201:enzymology*; D017506:H(+)-K(+)-Exchanging ATPase / Q000737:chemistry* / Q000502:physiology; D007093:Imidazoles / Q000494:pharmacology; D007425:Intracellular Membranes / Q000276:immunology; D008297:Male; D010042:Ouabain / Q000494:pharmacology*; D054328:Proton Pump Inhibitors; D051381:Rats; D017207:Rats, Sprague-Dawley; D000254:Sodium-Potassium-Exchanging ATPase; D013270:Stomach / Q000201:enzymology*; D013552:Swine; D014638:Vanadates / Q000494:pharmacology*
D000897:Anti-Ulcer Agents; D000911:Antibodies, Monoclonal; D027682:Cation Transport Proteins; D007093:Imidazoles; D054328:Proton Pump Inhibitors; C035235:Sch 28080; D014638:Vanadates; D010042:Ouabain; D000251:Adenosine Triphosphatases; C022761:potassium transporting ATPase; D017506:H(+)-K(+)-Exchanging ATPase; D000254:Sodium-Potassium-Exchanging ATPase