Tipton C M, Greenleaf J E, Jackson C G
Department of Physiology, University of Arizona, Tucson 85721-0093, USA.
Med Sci Sports Exerc. 1996 Aug;28(8):988-98. doi: 10.1097/00005768-199608000-00009.
Despite the fact that the first human was in space during 1961 and individuals have existed in a microgravity environment for more than a year, there are limited spaceflight data available on the responses of the neuroendocrine and immune systems. Because of mutual interactions between these respective integrative systems, it is inappropriate to assume that the responses of one have no impact on functions of the other. Blood and plasma volume consistently decrease with spaceflight; hence, blood endocrine and immune constituents will be modified by both gravitational and measurement influences. The majority of the in-flight data relates to endocrine responses that influence fluids and electrolytes during the first month in space. Adrenocorticotropin (ACTH), aldosterone, and anti-diuretic hormone (ADH) appear to be elevated with little change in the atrial natriuretic peptides (ANP). Flight results longer than 60 d show increased ADH variability with elevations in angiotensin and cortisol. Although post-flight results are influenced by reentry and recovery events, ACTH and ADH appear to be consistently elevated with variable results being reported for the other hormones. Limited in-flight data on insulin and growth hormone levels suggest they are not elevated to counteract the loss in muscle mass. Post-flight results from short- and long-term flights indicate that thyroxine and insulin are increased while growth hormone exhibits minimal change. In-flight parathyroid hormone (PTH) levels are variable for several weeks after which they remain elevated. Post-flight PTH was increased on missions that lasted either 7 or 237 d, whereas calcitonin concentrations were increased after 1 wk but decreased after longer flights. Leukocytes are elevated in flights of various durations because of an increase in neutrophils. The majority of post-flights data indicates immunoglobulin concentrations are not significantly changed from pre-flight measurements. However, the numbers of T-lymphocytes and natural killer cells are decreased with post-flight conditions. Of the lymphokines, interleukin-2 production, lymphocyte responsiveness, and the activity of natural killer cells are consistently reduced post-flight. Limited head-down tilt (HDT) data suggest it is an effective simulation model for microgravity investigations. Neuroendocrine and pharmacological countermeasures are virtually nonexistent and should become high priority items for future research. Although exercise has the potential to be an effective countermeasure for various neuroendocrine-immune responses in microgravity, this concept must be tested before flights to Mars are scheduled.
尽管1961年就有人类进入太空，且个体已在微重力环境中存在了一年多，但关于神经内分泌和免疫系统反应的太空飞行数据仍然有限。由于这些整合系统之间存在相互作用，因此不能假定一个系统的反应对另一个系统的功能没有影响。随着太空飞行，血液和血浆量持续减少；因此，血液中的内分泌和免疫成分会受到重力和测量影响的双重改变。大多数飞行中的数据涉及太空飞行第一个月内影响体液和电解质的内分泌反应。促肾上腺皮质激素（ACTH）、醛固酮和抗利尿激素（ADH）似乎升高，而心钠素（ANP）变化不大。超过60天的飞行结果显示，随着血管紧张素和皮质醇升高，ADH变异性增加。尽管飞行后的结果受重返大气层和恢复事件的影响，但ACTH和ADH似乎持续升高，而其他激素的结果则有变化。关于胰岛素和生长激素水平的飞行中数据有限，表明它们并未升高以抵消肌肉质量的损失。短期和长期飞行后的结果表明，甲状腺素和胰岛素增加，而生长激素变化最小。飞行中的甲状旁腺激素（PTH）水平在几周内变化不定，之后持续升高。在持续7天或237天的任务后，飞行后PTH升高，而降钙素浓度在1周后升高，但在更长时间飞行后降低。由于中性粒细胞增加，不同持续时间飞行中的白细胞都会升高。大多数飞行后数据表明，免疫球蛋白浓度与飞行前测量相比没有显著变化。然而，T淋巴细胞和自然杀伤细胞的数量在飞行后条件下会减少。在淋巴因子中，白细胞介素-2的产生、淋巴细胞反应性和自然杀伤细胞的活性在飞行后持续降低。有限的头低位倾斜（HDT）数据表明，它是微重力研究的有效模拟模型。神经内分泌和药物对策几乎不存在，应成为未来研究的高度优先项目。尽管运动有可能成为微重力下各种神经内分泌-免疫反应的有效对策，但在安排火星飞行之前，这一概念必须经过测试。
