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Low LBNP Tolerance in Men is Associated With Attenuated Activation of The Renin-Angiotensin SystemVasoactive hormone concentrations [epinephrine (pE), norepinephrine (pNE), angiotensin II (pATII), vasopressin (pVP), endothelin 1 (pET1)] and plasma renin activity (pRA) were measured during lower body negative pressure (LBNP) to test the hypothesis that responsiveness of the renin-angiotensin system is related to LBNP tolerance. Healthy men (2,822 cal/day(exp -1), 2 mmol*kg(exp -1)*day(exp -1)) Na(+)) were exposed to 30 minutes of progressive LBNP to -50 mmHg. LBNP was uneventful for seven men (25 +/- 2 years, HiTol group), but eight men (26 +/- 3 years) reached pre-syncope after 11 +/- 1 minutes (P < 0.001, LoTol group). Mean arterial pressure was unchanged. Central venous pressure and left atrial diameter decreased in both groups (5-6 mmHg by approx. 30%, P < 0.05). Control [hormone] were similar but, pRA differed between groups (LoTol 0.6 +/- 0.1, HiTol 1.2 +/- 0.1 ng Ang1/(ml(exp -1)*h(exp -1)), P < 0.05). LBNP increased (P < 0.05) pRA and pATII more in HiTol (9.9 +/- 2.2 ng Ang1/(ml(exp -1)*h(exp -1)) and 58 +/- 12 pg/ml(exp -1)) than LoTol (4.3 +/- 0.9 ng Ang1/(ml*h) and 28 +/- 6 pg/ml(exp -1)). In contrast, pVP was higher (P < 0.05) in LoTol than in HiTol. The response of the renin-angiotensin system seems linked to the occurrence of pre-syncope, and measurement of resting pRA may be predictive.
Document ID
20000118210
Acquisition Source
Ames Research Center
Document Type
Preprint (Draft being sent to journal)
Authors
Greenleaf, J. E.
(NASA Ames Research Center Moffett Field, CA United States)
Petersen, T. W.
(NASA Ames Research Center Moffett Field, CA United States)
Gabrielsen, A.
(NASA Ames Research Center Moffett Field, CA United States)
Pump, B.
(NASA Ames Research Center Moffett Field, CA United States)
Bie, P.
(NASA Ames Research Center Moffett Field, CA United States)
Christensen, N.-J.
(NASA Ames Research Center Moffett Field, CA United States)
Warberg, J.
(NASA Ames Research Center Moffett Field, CA United States)
Videbaeck, R.
(NASA Ames Research Center Moffett Field, CA United States)
Simonson, S. R.
(NASA Ames Research Center Moffett Field, CA United States)
Norsk, P.
(NASA Ames Research Center Moffett Field, CA United States)
Date Acquired
August 19, 2013
Publication Date
January 1, 1999
Subject Category
Aerospace Medicine
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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