Role of blood flow in gastric acid secretion.

The relationship between gastric acid secretion and blood flow has been investigated with a variety of different blood flow techniques including aminopyrine clearance, hydrogen gas clearance, intravital microscopy, laser-Doppler flowmetry, radioactive microspheres, and the elimination of inert gases. The most commonly used technique, aminopyrine clearance, predicts that increasing acid secretion is accompanied by a parallel increase in blood flow. However, the efficiency of clearance of aminopyrine is low in the nonsecreting stomach and increases as secretion rate increases. This precludes the use of aminopyrine clearance as a reliable measure of gastric mucosal blood flow at all but the highest steady-state level of acid secretion and casts doubt on the findings with this technique. Other methods for measuring blood flow indicate that there is no simple relationship between secretion and flow, with some studies finding that secretion and flow change in parallel and others finding that secretion varies quite independently of flow to the mucosa. One consistent finding is a strong correlation between stimulated acid secretion and gastric oxygen consumption. Both acid secretion and oxygen consumption fall if celiac blood flow is reduced below a critical value, which in the anesthetized dog stomach is approximately 30-40 ml.min-1.100 g-1. Driving blood flow above this value does not increase oxygen consumption and acid secretion, i.e., they reach a plateau. The shape of this relationship with its flow-dependent and flow-independent portions is used to explain the apparently contradictory findings in the literature regarding gastric acid secretion and blood flow.