[Effects of acute hypobaric hypoxia on gastric emptying and intestinal propulsion: experiment with rats].

Objective: To investigate the impact of acute hypobaric hypoxia on the gastrointestinal motility.

Methods: Eighty Wistar rats were randomly divided into 4 equal groups to be fed with (99)Tc(m)-labeled test food: ground level control group, put in the hypobaric chamber for 30 minutes; 3000 m simulated altitude group, exposed to the environment of simulated altitude of 3000 m for 30 minutes; 5000 m simulated altitude group, exposed to the environment of simulated altitude of 5000 m for 30 minutes; and mosapride + 5000 m simulated altitude group, fed with mosapride 2 mg/kg by perfusing stomach and fed with isotope-labeled test food 30 minutes later, and then exposed to 5000 m simulated altitude for 30 minutes. By the end of experiment the rats were killed, their stomachs were taken out to calculate the gastric emptying rate. Their intestine from pylorus to ileocecum was taken out to measure the intestinal propulsion function by using charcoal particle method. At the beginning and at the end of experiment abdominal arterial blood samples were collected to detect the plasma motilin and nitric oxide (NO) concentrations.

Results: The gastric emptying rate of the 5000 m simulated altitude group was 41% +/- 10%, significantly lower than that of the ground level group (62% +/- 12%, P < 0.01), and the charcoal transit rate of the 5000 m simulated altitude group was 37% +/- 8%, significantly lower than that of the ground level group (61% +/- 13%, P < 0.01). The gastric emptying rate and intestine propulsion rate of the 3000 m simulated altitude group were not significantly different from those of the ground level group. The gastric emptying rate of the mosapride + 5000 m simulated altitude group was 55% +/- 12%, significantly higher than that of the 5000 m simulated altitude group (P < 0.05), however, the intestine propulsion rate of the mosapride + 5000 m simulated altitude group was not significantly different from that of the 5000 m simulated altitude group (P > 0.05). The plasma motilin level of the 5000 m simulated altitude group was 88 pg/ml +/- 19 pg/ml, significantly lower than that of the ground level group (123 pg/ml +/- 28 pg/ml, P < 0.01), in contrast, the plasma NO level of the 5000 m simulated altitude group was 106 micromol/L +/- 24 micromol/L, significantly higher than that of the ground level group (80 micromol/L +/- 18 micromol/L, P < 0.01).

Conclusion: Acute exposure to hypobaric hypoxia at the height of 5000 m inhibits the gastric emptying and intestinal propulsion. Mosapride may alleviate the inhibitory effect of hypobaric hypoxia on gastric emptying. Decrease of plasma motilin and elevation of NO level may be the main mechanism of inhibition of gastrointestinal motility by hypobaric hypoxia.