Chemicals bathing the oxyntic gland area stimulate acid secretion in dog

Abstract

Release of gastrin is the only recognized mechanism by which chemicals in the stomach stimulate acid secretion. We report here that dietary components coming in contact only with oxyntic gland mucosa stimulate near maximal acid secretion through a local, H-sensitive mechanism that does not involve gastrin. In 4 dogs with gastric fistula and Heidenhain pouch (HP), 10% liver extract, 10% peptone, 0.4 M glycine, or Tris buffer, as control, was instilled into the HP in volumes of 40, 80, or 160 ml every 30 min. Instilled solutions were adjusted to pH 8.0 and HP acid secretion was measured by titrating a sample of the fluid recovered from the HP back to pH 8.0 with 0.2 M NaOH. Instillation of liver extract into the HP stimulated acid secretion from the HP but caused no change in serum gastrin and no change in acid secretion from the gastric fistula. The maximal response to liver extract occurred with the largest volume instilled and was 80% of the maximal response to histamine and 188% of the maximal response to pentagastrin. Expressed as per cent of maximal response to histamine, the maximal response to Tris buffer was 8%, to peptone 44%, and to glycine 14%. Intact bovine serum albumin gave no response, but after digestion by pepsin it stimulated acid secretion moderately. At pH 2.0, liver extract caused no stimulation of acid secretion. The pH threshold was about 2.5, and at pH 4.5 acid secretion was 55% of the response at pH 8.0. The response to liver extract at pH 8.0 was only minimally decreased by topical lidocaine or by intravenous atropine or metiamide. Since atropine and metiamide almost totally abolish the acid response to food in the main stomach, but do not inhibit secretion of acid evoked by instilling liver extract into the HP, there is reason to doubt whether this new mechanism operates under physiological conditions.