Drummer C, Gerzer R, Baisch F, Heer M
Institut für Luft-und Raumfahrtmedizin, Deutsches Zentrum für Luft-und Raumfahrt, Cologne, Germany.
Pflugers Arch. 2000;441(2-3 Suppl):R66-72. doi: 10.1007/s004240000335.
Similar to the response to central hypervolemic conditions on Earth, the shift of blood volume from the legs to the upper part of the body in astronauts entering micro-gravity should, in accordance with the Henry-Gauer mechanism, mediate diuresis and natriuresis. However, fluid balance and kidney function experiments during various space missions resulted in the surprising observation that the responses qualitatively differ from those observed during simulations of hypervolemia on Earth. There is some evidence that the attenuated responses of the kidney while entering weightlessness, and also later during space flight, may be caused by augmented fluid distribution to extravascular compartments compared to conditions on Earth. A functional decoupling of the kidney may also contribute to the observation that renal responses during exposure to micro-gravity are consistently weaker than those during simulation experiments before space flight. Deficits in body mass after landing have always been interpreted as an indication of absolute fluid loss early during space missions. However, recent data suggest that body mass changes during space flight are rather the consequences of hypocaloric nutrition and can be overcome by improved nutrition schemes. Finally, sodium-retaining humoral systems are activated during space flight and may contribute to a new steady-state of metabolic balances with a pronounced increase in body sodium compared to respective conditions on Earth. A revision of the classical "micro-gravity fluid shift" scheme is required.
与地球上对中枢性血容量过多情况的反应类似，根据亨利 - 高尔机制，进入微重力环境的宇航员体内血容量从腿部向身体上部转移时，应介导利尿和利钠作用。然而，在各种太空任务期间进行的液体平衡和肾功能实验得出了惊人的观察结果，即这些反应在性质上与在地球上模拟血容量过多时观察到的反应不同。有证据表明，进入失重状态时以及在太空飞行后期肾脏反应减弱，可能是因为与地球上的情况相比，血管外间隙的液体分布增加。肾脏的功能解耦也可能导致这样的观察结果：在暴露于微重力环境期间的肾脏反应始终比太空飞行前的模拟实验中的反应弱。着陆后体重减轻一直被解释为太空任务早期绝对液体流失的迹象。然而，最近的数据表明，太空飞行期间的体重变化更多是低热量营养的结果，并且可以通过改进营养方案来克服。最后，太空飞行期间钠潴留体液系统被激活，可能导致代谢平衡达到新的稳态，与地球上的相应情况相比，体内钠含量显著增加。需要对经典的“微重力液体转移”方案进行修订。
