Vasoactive neuroendocrine responses associated with tolerance to lower body negative pressure in humans.

摘要: The purpose of this investigation was to test the hypothesis that peripheral vasoconstriction and orthostatic tolerance are associated with increased circulating plasma concentrations noradrenaline, vasopressin renin-angiotensin. Sixteen men were categorized as having high (HT, n=9) or low (LT, n=7) lower body negative pressure (LBNP) based on whether endpoint their pre-syncopal-limited LBNP (peak LBNP) exposure exceeded -60 mmHg. two groups matched for age, height, weight, leg volume, blood volume maximal oxygen uptake, well baseline vasoactive hormones. Peak induced similar reductions in mean arterial both groups. reduction pulse (measured by impedance rheography), an index vascular constriction, from peak greater (P<0.05) HT group (-0.041 +/- 0.005 ml 100 ml-1) compared LT (-0. 025 0.003 ml-1). Greater higher average elevations (pVP, Delta=+7.2 2.0 pg renin-angiotensin (PRA, Delta=+2.9 1.3 ng Ang II ml-1 h-1) pVP (+2.2 1.0 PRA (+0.1 0.1 group. Plasma noradrenaline groups, no statistically distinguishable difference between These data suggest systems may contribute sustaining vasoconstrictive actions.