Blood flow limitation of stimulated gastric acid secretion in the rat

Secretagogue-stimulated gastric acid output is reduced when gastric mucosal blood flow is below normal. We tested the hypothesis that the reduction in acid secretion associated with reduced mucosal blood flow was due to a decrease in the delivery of the secretagogue. Gastric acid output was determined by continuous gastric lavage with 0.15 M NaCl, and gastric corpus mucosal blood flow was measured by hydrogen gas clearance in anesthetized, pylorus-ligated rats before and during a period of hypovolemia-induced reduction in mucosal blood flow. A linear correlation between pentagastrin- and histamine-stimulated gastric acid output and gastric corpus mucosal blood flow during hypotension over a range of mucosal blood flow rates was found, and each was expressed as a percentage of the plateau values before hemorrhage. When the dose of pentagastrin was doubled or tripled, or when the stimulation of gastric acid secretion was vagus nerve stimulation, a stimulant of acid secretion that is independent of blood flow for secretatogue delivery, the reduction in gastric acid output by hypotension was not reversed. We conclude that stimulated gastric acid secretion during hemorrhagic hypotension is blood flow-limited and not related to inadequate delivery of secretagogue to parietal cells.