Intestinal phase of gastric acid secretion in humans with and without portacaval shunt

To examine the effect of proximal small intestinal stimulants of gastric acid secretion in cirrhotic patients with portacaval shunt, unshunted cirrhotics, and normal subjects, a mixture of L-amino acids was administered intraduodenally, into the proximal jejunum, or intravenously to 8 cirrhotic patients with portacaval shunt and to 8 unshunted subjects (4 cirrhotic and 4 healthy volunteers). In addition, the effect of intrajejunally administered hyperosmolar mannitol (850 mosmol/kg) and intrajejunal balloon distention (40 mmHg) was determined. In the shunted and unshunted groups gastric acid secretion significantly increased equally in response to intravenous and intraduodenal amino acid infusion, whereas amino acids administered intrajejunally did not significantly alter acid secretion. Perfusion of the jejunum with hyperosmolar mannitol resulted in significant stimulation of acid secretion in the shunted subjects, whereas in the unshunted subjects it caused significant inhibition. In addition, jejunal balloon distention significantly stimulated secretion in the shunted subjects, but not in the unshunted group. Serum gastrin did not change significantly during any of the experiments and plasma amino acids were not different after jejunal compared with duodenal perfusion. These studies indicate the following: Enteral and parenteral amino acids increase gastric acid secretion similarly in subjects with and without portacaval shunt. The intestinal phase of gastric acid secretion is initiated by intraduodenal, but not intrajejunal, amino acids. As plasma amino acid concentrations were similar regardless of the route used, this suggests that the intestinal phase of acid secretion cannot be fully explained by the postabsorptive stimulation by amino acids. Intrajejunal distention with a balloon or infusion of hyperosmolar mannitol into the proximal jejunum stimulates acid secretion only in subjects with portacaval shunt.