间断性头高位45°对模拟失重兔颈静脉及肠系膜静脉顺应性的影响

Effects of intermittent 45° head-up tilt on compliance of jugular vein and mesenteric vein in rabbits after simulated weightlessness

目的: 观察 21d模拟失重及间断性头高位 45°对兔颈静脉及肠系膜静脉顺应性的影响. 方法: 健康雄性新西兰兔 24只,随机分为对照组、模拟失重组和对抗组,每组 8只.模拟失重组在 21d实验期间保持头低位 -20°. 对抗组在 21d模拟失重期间每日 45°头高位倾斜 2h. 实验后测试离体颈静脉及肠系膜静脉的拉伸 载荷关系. 结果: 在同等载荷情况下,模拟失重组颈静脉形变较对照组均显著减小 (P<0. 05或P<0. 01),肠系膜静脉均显著增大 (P<0. 01 ). 对抗组颈静脉及肠系膜静脉形变较对照组均无明显差异;而较模拟失重组颈静脉形变显著增大 (P<0. 05或P<0. 01),肠系膜静脉形变显著减小(P<0. 05 ). 结论: 21d模拟失重可引起兔颈静脉顺应性显著减小,肠系膜静脉顺应性显著增加,每日 2h头高位 45°可对抗 21d模拟失重所引起的兔颈静脉和肠系膜静脉顺应性的变化.

AIM: To observe the effects of simulated weightlessness and intermittent head-up-tilt 45° on the compliance of jugular and mesenteric vein in rabbits. METHODS: Twenty-four healthy male rabbits were randomly divided into three groups: control group, simulated weightlessness group and countermeasure group, with 8 rabbits in each group. Simulated weightlessness group kept head-down tilt for 21 d. The countermeasure group kept head-up tilt 2 h every day during the 21 d head-down tilt. After 21 d experiment, the compression-displacement relationship of jugular and mesenteric vein strips and rings was observed. RESULTS: With the same compression, the displacement of jugular vein in the simulated weightlessness group decreased significantly compared with that in control group (P< 0.05 or P<0.01) and the displacement of mesenteric vein in simulated weightlessness group increased significantly compared with that control group (P<0.05). With the same compression, the displacement of both jugular vein and mesenteric vein in countermeasure group had no obvious difference from that of control group. With the same compression, the displacement of jugular vein in countermeasure group increased significantly compared with that in weightlessness group, but the displacement of mesenteric vein decreased significantly (P<0.05). CONCLUSION: A twenty-one-day simulated weightlessness may lead to a significant decrease of jugular venous compliance and an increase of mesenteric venous compliance in rabbits. Training of 45° head-up tilt 2 h per day can counteract the effects of simulated weightless on the mesenteric and jugular venous compliance.