Whitson P A, Cintron N M, Pietrzyk R A, Scotto P, Loeppky J A
Biomedical Operations and Research Branch NASA/Johnson Space Center, KRUG Life Sciences, Houston, Texas.
J Clin Pharmacol. 1994 May;34(5):427-33. doi: 10.1002/j.1552-4604.1994.tb04983.x.
In an effort to understand the interaction between acute postural fluid shifts and hypoxia on hormonal regulation of fluid homeostasis, the authors measured the responses to head-down tilt with and without acute exposure to normobaric hypoxia. Plasma atrial natriuretic peptide (ANP), cyclic guanosine monophosphate (cGMP), cyclic adenosine monophosphate (cAMP), plasma aldosterone (ALD), and plasma renin activity (PRA) were measured in six healthy male volunteers who were exposed to a head-down tilt protocol during normoxia and hypoxia. The tilt protocol consisted of a 17 degrees head-up phase (30 minutes), a 28 degrees head-down phase (1 hour), and a 17 degrees head-up recovery period (2 hours, with the last hour normoxic in both experiments). Altitude equivalent to 14,828 ft was simulated by having the subjects breathe an inspired gas mixture with 13.9% oxygen. The results indicate that the postural fluid redistribution associated with a 60-minute head-down tilt induces the release of ANP and cGMP during both hypoxia and normoxia. Hypoxia increased cGMP, cAMP, ALD, and PRA throughout the protocol and significantly potentiated the increase in cGMP during head-down tilt. Hypoxia had no overall effect on the release of ANP, but appeared to attenuate the increase with head-down tilt. This study describes the acute effects of hypoxia on the endocrine response during fluid redistribution and suggests that the magnitude, but not the direction, of these changes with posture is affected by hypoxia.
为了了解急性姿势性体液转移与低氧对体液平衡激素调节的相互作用，作者测量了在有和没有急性常压低氧暴露情况下，受试者对头低位倾斜的反应。在六名健康男性志愿者中测量了血浆心房利钠肽（ANP）、环磷酸鸟苷（cGMP）、环磷酸腺苷（cAMP）、血浆醛固酮（ALD）和血浆肾素活性（PRA），这些志愿者在常氧和低氧状态下接受头低位倾斜方案。倾斜方案包括17度头高位阶段（30分钟）、28度头低位阶段（1小时）和17度头高位恢复期（2小时，在两个实验中最后1小时为常氧）。通过让受试者呼吸含13.9%氧气的混合气体来模拟相当于14,828英尺的海拔高度。结果表明，与60分钟头低位倾斜相关的姿势性体液再分布在低氧和常氧状态下均诱导ANP和cGMP的释放。在整个方案中，低氧增加了cGMP、cAMP、ALD和PRA，并显著增强了头低位倾斜期间cGMP的增加。低氧对ANP的释放没有总体影响，但似乎减弱了头低位倾斜时ANP的增加。本研究描述了低氧对体液再分布期间内分泌反应的急性影响，并表明这些随姿势变化的幅度而非方向受低氧影响。
