Secretory surface area and phosphatase activity of frog gastric mucosa

Gastric mucosae were isolated from the European frog, R. temporaria, and after 5-7 h, stimulated with histamine (10(-4) M) and theophylline (5 mM). Acid secretion increased about fourfold, and this was accompanied by a threefold increase in secretory surface of the oxyntic cells, as determined in electron micrographs with conventional morphometric techniques. At the same time phosphatase activity of the secretory surface increased. Other experiments showed that the latter was due to an acid phosphatase, with pH optimum near 3. It appears that the increase in surface phosphatase with stimulation can be attributed to a diminished local pH and not to the increase in surface area demonstrated in this study.