Gastric Juice Acidity at the End of the Secretory Period.

Abstract

For many years, the theory of Heidenhain and of Pavlov—that the concentration of acid in the isolated parietal secretion is constant within narrow limits—was almost universally accepted. Most of the recent contributors, however, have taken the view that this fluid is a mixture of HCl and neutral chlorides, in varying proportions. The present paper is a refutation of one of the major arguments advanced by this latter group, 1 and deals with the decrease in acidity of the gastric juice during the latter part of the digestive period.

Variations in acidity of gastric juice are always observable, even in the relatively pure juice obtained from dogs with stomach pouches. Such variations were interpreted by Pavlov as resulting from partial neutralization by mucus. A major point in support of this explanation is the obvious parallelism of acidity and the rate of post-prandial secretion during any one experiment. In a previous communication, such correlation was confirmed 2 for food and small doses of histamine. When the gastric juice was collected by continuous drainage, samples being taken during quarter or half hour periods, it was observed that every increase or decrease in volume per period was accompanied by a like change in acidity. However, after increasing the rate of secretion sufficiently, as by the injection of a large dose of histamine, this parallelism vanished and the acidity became constant at a pH of 0.91. This is entirely in accord with Pavlov's conception.

In opposition to the theory, it was first suggested by Rosemann 3 and by Foster and Lambert 4 that the fluid secreted by the parietal cells possesses a fairly constant chloride content. With increased intensity of stimulation, and therefore increased rate of flow, the proportion of neutral chloride converted to acid is likewise increased, resulting in the commonly observed fluctuations in acidity.