The purpose of these studies was to determine the amount of saliva secreted in response to food in humans and to evaluate the effect of saliva on postprandial gastric acid secretion. Subjects chewed and spat out an appetizing steak and french-fried potato meal (modified sham feeding), with the increase in the weight of the meal during sham feeding taken to represent salivary secretion. Mean salivary flow rose from basal rates of 37.1 ml/h to 167.3 ml/h during modified sham feeding (P less than 0.001). Chewing gum increased salivary secretion to approximately the same extent as modified sham feeding, whereas chewing on plastic tubing caused a much smaller increase in salivary flow. Intravenous infusion of bethanechol (50 micrograms . kg-1 . h-1) was approximately half as potent as modified sham feeding or gum chewing in stimulating salivary flow. The salivary response to sham feeding was completely blocked by 15 micrograms/kg intravenous atropine. Salivary secretion increased approximately 20 ml/h when a 700-ml amino acid meal was infused directly into the stomach (P less than 0.01), whereas gastric distension with 700 ml saline had no effect. These findings suggested that food in the stomach or upper small intestine may activate a reflex or release a hormone into the circulation that augments salivary flow. Although intravenous gastrin-17 infusion had no effect on salivary flow, somatostatin-14 infusion increased salivary flow 15 ml/h (P less than 0.02). Saliva contained approximately 2,000 pg/ml immunoreactive urogastrone, an inhibitor of acid secretion when administered parenterally.(ABSTRACT TRUNCATED AT 250 WORDS)
The effect of strenuous physical exercise on postprandial gastric acid secretion and gastric emptying was evaluated in untrained healthy volunteers. Subjects exercised for 45 min on a stationary bicycle at 50 or 70% of their maximal work load, beginning 45 min after a steak meal. Compared with a control study during which subjects sat on the bicycle without exercising, exercise had no significant effect on the gastric acid secretory response to the meal (control, 31.9 +/- 8.3 mmol/120 min; exercise, 32.2 +/- 7.8 mmol/120 min) or on the amount of nonabsorbable meal marker that emptied from the stomach in 120 min (control, 88 +/- 3%; exercise, 87 +/- 4%). Increases in serum triglyceride levels after the meal were also unaffected by exercise, suggesting that absorption of dietary lipid was unimpaired by exercise. These studies indicate that strenuous exercise shortly after a meal has little effect on postprandial gastric secretory or motor function in humans.
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