Abstract
Adenosine triphosphatase (ATPase) activity was studied by histochemical methods in the gastric mucosa of Bufo spinulosus. Two types of activity were established. One is activated by Mg++, and is localized mainly at the intercellular boundaries and the basal zone of the oxyntic-peptic cells; the reaction products are found only on the outer side of the cells. The other is activated by HCO3 – and is mainly localized at the microvilli at the apical zone of the oxyntic-peptic cells. The intensity and/or distribution of the reactions are influenced by histamine stimulation. Control experiments demonstrated that: the microsomal fraction of gastric mucosa contained a Mg++-requiring ATPase activity which was enhanced by addition of HCO3 –; 25% of the ATPase activity of fresh tissue was maintained after fixation and incubation in presence of lead ion; the medium employed in the histochemical studies did not enhance the lead-catalyzed, nonenzymatic hydrolysis of ATP by more than 20% when compared with spontaneous ATP hydrolysis; and incubation in media with different ATP-Pb ratios did not significantly alter the location of the staining.