Leach C S, Johnson P C, Rambaut P C
Aviat Space Environ Med. 1976 Apr;47(4):402-10.
This study conducted on the crewmembers of Skylab 3 was designed to evaluate the endocrinological adaption resulting from extend exposure to a space flight environment by identifying changes in hormonal and associated fluid and electrolyte parameters. The three men served as their own controls and were on a constant dietary intake. Complete metabolic collections were performed beginning 21 d before the flight, continuing throughout the flight, for 18 d postflight. Changes in fluid and electrolyte balance have been correlated with weight loss, changes in the excretion of aldosterone, vasopressin, and fluid compartments. Inter-individual variability was demonstrated in most experimental indices measured; however, statistically significant patterns have emerged which include: decreases in body weight and ADH, increases in plasma renin activity, and elevations in urinary catecholamines, aldosterone and cortisol concentrations. Urinary sodium was increased in flight but potassium was only slightly changed. Total body exchangeable K was slightly decreased in all three of the crewmen. Total body water and extracellular fluid were decreased postflight in almost all cases. The measured changes are consistent with the prediction that a relative increase in thoracic blood volume upon transiton to the zero gravity environment is interpretated as a true volume expasion resulting in a net fluid loss. This, in association with other factors, ultimately results in a reduction in intravascular volume leading to an increase in renin and a secondary aldosteronism. Once these compensatory mechanisms are effective in reestablishing positive water balance, the crewemn are considered to be essentially adapted to the space environment. Although the physiological cost of this adaptation must reflect the electrolyte deficit and perhaps other factors, it is assumed that the compensated state is adequate for the demands of the environment; however, this new homeostatic set is not believed to be without physiological cost and could, except with proper precautions, reduce the functional reserve of exposed individuals.
这项针对天空实验室3号机组人员开展的研究，旨在通过识别激素及相关体液和电解质参数的变化，评估因长期暴露于太空飞行环境而产生的内分泌适应性。这三名男性以自身作为对照，且饮食摄入保持恒定。从飞行前21天开始，在整个飞行过程中以及飞行后18天进行完整的代谢物收集。体液和电解质平衡的变化与体重减轻、醛固酮、血管加压素排泄变化以及体液区室变化相关。在大多数测量的实验指标中都表现出个体间差异；然而，已出现具有统计学意义的模式，包括：体重和抗利尿激素减少、血浆肾素活性增加、尿儿茶酚胺、醛固酮和皮质醇浓度升高。飞行过程中尿钠增加，但钾仅有轻微变化。所有三名机组人员的全身可交换钾均略有减少。几乎在所有情况下，飞行后总体水和细胞外液均减少。所测得的变化与以下预测一致，即过渡到零重力环境时胸腔血容量的相对增加被解释为真正的容量扩张，导致净体液流失。这与其他因素一起，最终导致血管内容量减少，从而导致肾素增加和继发性醛固酮增多症。一旦这些代偿机制有效地重新建立正水平衡，机组人员就被认为基本适应了太空环境。尽管这种适应的生理代价必定反映了电解质缺乏以及可能的其他因素，但假定代偿状态足以满足环境需求；然而，这种新的稳态设定并非没有生理代价，并且如果没有适当的预防措施，可能会降低暴露个体的功能储备。
