Changes in gastric mucosa, submucosa, and muscularis IC pH may herald irreversible tissue injury.

Previously we noted an abrupt rise in gastric intracellular pH (IC pH) and bicarbonate buffering between 15 and 30 min of cardiac arrest which we termed agonal alkalinization, failure of pH regulation. Agonal alkalinization may represent the transition point between reversible and irreversible injury. We asked the question, what is the sequence of change in IC pH within the gastric layers, mucosa, submucosa, and muscularis, and which layer is most sensitive? This research explored changes in IC pH within the stomach layers, mucosa, submucosa, and muscularis, at 0, 5, 15, 30, and 40 min, under three conditions, normoxia (control), ischemia (cardiac arrest), and eucapnic hypoxia (12 % oxygen). The mucosa was the most alkalotic gastric layer at baseline. Ischemia and hypoxia at 40″ produced different layer responses with the mucosa and submucosa the most sensitive layers during ischemia and the muscularis during hypoxia. Further study to examine the mechanism of changes between gastric layers using spatial-temporal techniques may assist in understanding the transition to irreversible injury.