Plasma Renin Activity and Aldosterone: Correlations with Moderate Hypohydration

摘要

Adult male test subjects were assigned to one of three clothing configurations (Army fatigues, fatigues with chemical protective garments, and fatigues with protective garments plus protective masks) prior to exercise (level treadmill, 1.11 m/s, 50 min/h, 6h) in a moderate (WBGT=23 C) environment with ad lib water consumption. Antecubital blood samples were taken prior to the start of and subsequent to the completion of exercise and analyzed for fluid-electrolyte regulatory hormones. During all trials with chemical protective garments, plasma renin activity (PRA) and aldosterone levels (PA) were significantly elevated following the exercise protocol while neither was affected during exercise in fatigues only. Individual hypohydration levels during all trials ranged from low to moderate. Levels of PRA were closely correlated with hypohydration as measured by percentage of body weight lost during the 6 h trial. Likewise, PA was also correlated with body weight loss. We concluded from this study that PRA and PA responses were exacerbated in moderate environments by the additional heat stress of impermeable garments. Further, the logistical difficulty inherent in delivering fluid through the chemical protective mask reduced voluntary consumption, increased hypohydration, and elicited the greatest elevations in PRA and PA. Finally, even at these modest levels of hypohydration, the intensity of the PRA and PA responses were correlated with hypohydration level (AW)