Gastric and pancreatic responses to meals varying in pH

1. Gastric acid response to a test meal of 10% peptone was measured in chronic gastric and pancreatic fistula cats using the Fordtran and Walsh method, monitoring the rate at which a solution of 0.5 M sodium bicarbonate had to be added to maintain constant pH of gastric content at pre-selected values ranging from 5.0 to 1.0. Simultaneously, pancreatic secretion was determined by the standard collection technique. In this way the pH profile for the inhibition of gastric secretion and stimulation of pancreatic secretion has been established in cats.2. A peptone meal adjusted to pH 5.0 produced gastric acid output similar to the maximal response to histamine or pentagastrin. It provoked a negligible stimulation of pancreatic flow rate and bicarbonate output but a large protein output.3. Graded decrease of the peptone meal pH to below 4.0 resulted in inhibition of gastric acid production and in a concomitant stimulation of pancreatic secretory volume and bicarbonate output. A meal adjusted to pH 1.0 stimulated gastric secretion only about 30% of the response recorded at pH 5.0. Pancreatic secretion with a meal adjusted to pH 3.0 reached the highest level of about 70% of the maximal response to exogenous secretin.4. Since the observed changes in the secretory activity of the stomach and the pancreas induced by test meals adjusted to pH 3.0 can be fully reproduced by exogenous secretin, it is suggested that in the cat this hormone may be responsible for the gastric inhibitory and pancreatic stimulatory mechanisms activated during normal digestion of food.