HISTAMINE-INDUCED GASTRIC-ACID SECRETION IN HORSES

Objective-To determine gastric secretory responses in horses treated w ith histamine and to determine the dose of histamine needed to elicit maximal gastric secretion. Animals-6 adult horses with an indwelling g astric cannula. Procedure-Gastric contents were collected in 15-minute periods, and volume, pH, hydrogen ion concentration, hydrogen ion out put, sodium concentration, and sodium output were determined. Values w ere determined without any treatment (baseline), after administration of pyrilamine maleate (1 mg/kg of body weight, IV, given during a 15-m inute period), and during 1-hour infusions of histamine at 3 rates (7. 5, 15, and 30 mu g/kg/h, IV). Results-Volume and hydrogen ion concentr ation of gastric contents and hydrogen ion output were significantly i ncreased, compared with baseline values, during histamine infusion. Me an hydrogen ion concentration and hydrogen ion output were significant ly greater during infusion of histamine at a rate of 15 or 30 mu g/kg/ h than at a rate of 7.5 mu g/kg/h. Sodium concentration was significan tly decreased, compared with baseline value, during histamine infusion , but sodium output was unchanged. Conclusions-Histamine at doses of 1 5 and 30 mu g/kg/h. IV stimulated maximal gastric secretion in horses. Histamine appeared to induce only parietal secretion. Clinical Releva nce-This study provides additional information related to equine gastr ic physiology, which may benefit further understanding of the pathogen esis of peptic ulcer disease.