急性低压低氧对大鼠胃排空和小肠推进运动的影响

目的观察低压低氧对胃排空和小肠运动的作用,为阐明飞行因素对胃肠动力的影响提供理论依据。方法应用同位素~(99)Tc~m-SC 测定胃排空,炭末法测定小肠推进率。8组大鼠(每组10只)分别在低压舱海平面、模拟升至3000 m 和5000 m 高空停留30 min,测定大鼠胃排空率和小肠推进运动,并给予促动力药物莫沙比利观察对高空状态胃肠动力的影响。各组分别抽取动脉血测定血浆胃动素和一氧化氮的浓度。结果在模拟5000 m 高度状态,大鼠胃排空率和小肠推进率分别为41％±10％和37％±8％,明显低于地面组(分别为62％±12％和6l％±13％,均 P<0.01);模拟3000 m 高度对大鼠胃排空和小肠推进率无明显影响;口服莫沙比利组在5000 m 高度的胃排空率明显高于5000 m 对照组(55％±12％ vs 40％±10％,P<0.05),而对小肠推进率无明显影响;模拟5000 m 高度时大鼠血浆胃动素浓度明显低于地面组(88 pg/ml±19 pg/ml vs 123 pg/ml±28 pg/ml,P<0.01),而血浆一氧化氮浓度则明显高于地面组(106 μmol/L±24 μmol/L vs 80 μmol/L±18 μmol/L,P<0.01)。结论急性低压低氧抑制了胃排空和小肠推进运动,促动力药物莫沙比利可以减轻低压低氧抑制胃排空的作用。血浆胃动素浓度降低而一氧化氮浓度升高可能是低压低氧条件下胃肠动力减弱的主要机制。

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.