Effect of ranitidine on gastric acid secretion in young male horses

SUMMARY Gastric cannulas were placed surgically in 5 young male horses. After a 2-week recovery period, horses were studied once a week. Horses were fasted for 24 hours, and gastric fluid output was collected for 5 continuous hours. Volumes were recorded every 15 minutes, and pH and hydrogen ion concentration were determined in an aliquot from each period. In 10 basal experiments, using 5 horses, volume, pH, and hydrogen ion concentration were continuously variable. Mean acid output was 45.1 ± 2.02 μEq/15 min/kg (mean ± sem). In 6 experiments, using 3 horses, 0.5 mg of ranitidine/kg of body weight, given as an rv bolus after a 1-hour basal collection, significantly (P < 0.02) inhibited hourly total acid output for 4 hours, but did not significantly change pH. The cannulation technique was done without complications, and horses tolerated the cannula for several months. Seemingly, the horse has a continuously variable gastric acid secretion, and histamine type-2 receptors have a role in this process.