In Vivo Measurement of Gastric Mucus pH in Canines: Effect of High Luminal Acidity and Prostaglandin E2

Abstract

We measured gastric mucus pH in vivo in a canine chambered stomach preparation using glass pH microelectrodes. The average maximum mucus pH was 6.52 at a luminal pH of 3.0, declining gradually as luminal pH was lowered; the mucus pH gradient was obliterated completely when luminal pH reached 1.1. At a luminal pH of 1.0, the average maximum mucus pH increased to 6.03, whereas transmural potential dropped from -50.3 to -31.8 mV. Prostaglandin E2 pretreatment (10 μg/ml) prevented epithelial injury during exposure to 100 mM HCl, but mucus pH was unchanged as compared with the acid-only group (4.77 vs. 4.72, p = 0.92). Histology on stomachs exposed to a luminal pH of 1.0 revealed characteristic changes of superficial epithelial injury without affecting the deeper gastric glands or disrupting the basal lamina. Prostaglandin E2 pretreatment prevented these histologic changes. These results indicate that although the mucus pH gradient can be overwhelmed by high luminal acidity, a newly formed mucus pH gradient may develop after disruption of epithelial integrity, possibly providing protection for the mucosa during the period of epithelial repair. The high mucus pH (4.77) accompanying normal histology and unchanged potential suggests that prostaglandin E2 may protect the surface epithelium by the stimulation of bicarbonate secretion.