CNRS UMR - INSERM U, Faculté de Médecine d'Angers, France.
Auton Neurosci. 2011 Feb 24;160(1-2):64-8. doi: 10.1016/j.autneu.2010.10.003. Epub 2010 Nov 11.
Actual and simulated microgravity induces hypovolemia and cardiovascular deconditioning, associated with vascular dysfunction. We hypothesized that vasoconstriction of skin microcirculatory bed should be altered following 7 days of simulated microgravity in order to maintain cardiovascular homeostasis during active standing. Eight healthy men were studied before and after 7 days of simulated microgravity modeled by dry immersion (DI). Changes of plasma volume and orthostatic tolerance were evaluated. Calf skin blood flow (laser-Doppler flowmetry), ECG and blood pressure signal during a 10-min stand test were recorded, and skin vascular resistance, central hemodynamics, baroreflex sensitivity and heart rate variability were estimated. After DI we observed increased calf skin vascular resistance in the standing position (12.0 ± 1.0 AU-after- vs. 6.8 ± 1.4 AU-before), while supine it was unchanged. Cardiovascular deconditioning was confirmed by greater tachycardia on standing and by hypovolemia (-16 ± 3% at day 7 of DI). Total peripheral resistance and indices of cardiovascular autonomic control were not modified. In conclusion, unchanged autonomic control and total peripheral resistance suggest that increased skin vasoconstriction to standing involves rather local mechanisms-as venoarteriolar reflex-and might compensate insufficient vasoconstriction of other vascular beds.
实际和模拟微重力会引起血容量减少和心血管功能下降，伴随着血管功能障碍。我们假设，在模拟微重力 7 天后，皮肤微循环床的血管收缩应该会发生改变，以在主动站立时维持心血管稳态。8 名健康男性在模拟微重力（干式浸浴）7 天后进行了前后对比研究。评估了血浆容量和直立耐力的变化。在 10 分钟站立测试期间记录了小腿皮肤血流（激光多普勒血流仪）、心电图和血压信号，并估算了皮肤血管阻力、中心血液动力学、压力反射敏感性和心率变异性。在 DI 后，我们观察到站立位小腿皮肤血管阻力增加（12.0 ± 1.0 AU-后 vs. 6.8 ± 1.4 AU-前），而仰卧位则不变。心血管功能下降通过站立时心动过速和血容量减少（DI 第 7 天减少 16 ± 3%）得到证实。总外周阻力和心血管自主控制指数没有改变。总之，自主控制和总外周阻力不变表明，站立时皮肤血管收缩增加涉及到局部机制，如静脉血管反射，可能会补偿其他血管床的血管收缩不足。
