A monoclonal antibody (mAb 95-111) was used to titrate the amounts of H+/K(+)-ATPase in subcellular fractions of the fundus of rats, pigs, rabbits and humans. All four had similar amounts of H+/K(+)-ATPase: 2.1 +/- 0.5 (human), 1.9 +/- 0.4 (rabbit), 4.4 +/- 0.5 (rat) and 4.2 +/- 0.8 (hog) mg ATPase/g wet tissue. The antigen concentrations and H+/K(+)-ATPase enzymatic activities of subcellular fractions were linearly correlated in all species but rat suggesting that human, rabbit and hog H+/K(+)-ATPases have similar rates of catalysis (223 mumol Pi/h per mg ATPase). The non-correlation of rat data probably reflects the known lability of the rat enzyme. Hence, immuno-titration promises to be a more reliable method of estimating rat ATPase than the currently used enzymatic assay. The H+/K(+)-ATPase content of human biopsies was 20-fold higher than previously-published (Smolka, A. and Weinstein, W.M. (1986) Gastroenterology 90, 532-539) suggesting that the previous immuno-titration underestimated the H+/K(+)-ATPase content of the human fundus.
Adenosine Triphosphatases Animals