Tou Janet, Ronca April, Grindeland Richard, Wade Charles
Lockheed Martin Sciences and Engineering, NASA Ames Research Center, Moffett Field, California 94035, USA.
Biol Reprod. 2002 Dec;67(6):1681-7. doi: 10.1095/biolreprod.102.007252.
Mammalian reproduction evolved within Earth's 1-g gravitational field. As we move closer to the reality of space habitation, there is growing scientific interest in how different gravitational states influence reproduction in mammals. Habitation of space and extended spaceflight missions require prolonged exposure to decreased gravity (hypogravity, i.e., weightlessness). Lift-off and re-entry of the spacecraft are associated with exposure to increased gravity (hypergravity). Existing data suggest that spaceflight is associated with a constellation of changes in reproductive physiology and function. However, limited spaceflight opportunities and confounding effects of various nongravitational factors associated with spaceflight (i.e., radiation, stress) have led to the development of ground-based models for studying the effects of altered gravity on biological systems. Human bed rest and rodent hindlimb unloading paradigms are used to study exposure to hypogravity. Centrifugation is used to study hypergravity. Here, we review the results of spaceflight and ground-based models of altered gravity on reproductive physiology. Studies utilizing ground-based models that simulate hyper- and hypogravity have produced reproductive results similar to those obtained from spaceflight and are contributing new information on biological responses across the gravity continuum, thereby confirming the appropriateness of these models for studying reproductive responses to altered gravity and the underlying mechanisms of these responses. Together, these unique tools are yielding new insights into the gravitational biology of reproduction in mammals.
哺乳动物的繁殖是在地球1g重力场中进化而来的。随着我们越来越接近太空居住的现实，科学界对不同重力状态如何影响哺乳动物繁殖的兴趣日益浓厚。太空居住和长期太空飞行任务需要长时间暴露在低重力环境（微重力，即失重）中。航天器的发射和重返大气层与暴露在高重力环境（超重）中有关。现有数据表明，太空飞行与生殖生理和功能的一系列变化有关。然而，有限的太空飞行机会以及与太空飞行相关的各种非重力因素（如辐射、压力）的混杂效应，促使人们开发基于地面的模型来研究重力改变对生物系统的影响。人体卧床休息和啮齿动物后肢卸载范式用于研究微重力暴露。离心法用于研究超重。在此，我们综述了太空飞行和基于地面的重力改变模型对生殖生理影响的研究结果。利用模拟超重和微重力的基于地面的模型进行的研究产生了与太空飞行相似的生殖结果，并为整个重力连续体上的生物反应提供了新信息，从而证实了这些模型对于研究重力改变的生殖反应及其潜在机制的适用性。这些独特的工具共同为哺乳动物繁殖的引力生物学带来了新的见解。
