hkatpase contents of human rabbit hog and rat gastric mucosa a monoclonal antibody mab 95111 was used to titrate the amounts of hkatpase in subcellular fractions of the fundus of rats pigs rabbits and humans all four had similar amounts of hkatpase 21 05 human 19 04 rabbit 44 05 rat and 42 08 hog mg atpaseg wet tissue the antigen concentrations and hkatpase enzymatic activities of subcellular fractions were linearly correlated in all species but rat suggesting that human rabbit and hog hkatpases have similar rates of catalysis 223 mumol pih per mg atpase the noncorrelation of rat data probably reflects the known lability of the rat enzyme hence immunotitration promises to be a more reliable method of estimating rat atpase than the currently used enzymatic assay the hkatpase content of human biopsies was 20fold higher than previouslypublished smolka a and weinstein wm 1986 gastroenterology 90 532539 suggesting that the previous immunotitration underestimated the hkatpase content of the human fundus