Gastric emptying of organic acids in the dog.

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Abstract
Test meals of 300 ml of 6 different organic acids were instilled into the stomach of 6 healthy mongrel dogs. Citric, acetic, propionic, lactic, tartaric and succinic acid were given in 50, 100, 150 and 200 mN concentrations. During the emptying process, the gastric contents were aspirated and immediately re-instilled at 10 min intervals, and the following parameters were recorded: volume, concentration of the organic anion, pH, H+ concentration and osmolarity. By multiple stepwise regression analysis, the combination of parameters which most effectively determines gastric emptying rate was concentration of the organic anion, followed by intragastric volume and number of previous test meals given on the same day. These 3 parameters appear in the equation for gastric emptying rate in which the individual characteristic of each acid is expressed by a constant. Among the various acids, inhibition of emptying rate increases with rising number of carboxylic groups of the acid and its molecular weight. After proximal gastric vagotomy, emptying rate of organic acids is independent of volume, and emptying approaches an exponential pattern. A model for gastric emptying of organic acids with at least 3 different receptors is proposed: 1 for the structure of the organic acid, 1 for concentration and 1 for intragastric volume.