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Low LBNP Tolerance in Men is Associated With Attenuated Activation of 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 reninangiotensin system is related to LBNP tolerance. Healthy men (2,822 cal per day, 2 mmol per kilogram per day Na (+)) were exposed to 30 min of progressive LBNP to -50mmHg. LBNP was uneventful for 7 men (2512 yr, HiTol group), but 8 men (26 plus or minus 3 yr) reached pre-syncope after 11 plus or minus 1 min (P less than 0.001, LoTol group). Mean arterial pressure was unchanged. Central venous pressure and left atrial diameter decreased in both groups (5-6 mmHg by 30%, P less than 0.05). Control [hormone] were similar but, pRA differed between groups (LoTol 0.6 plus or minus 0.1, HiTol 1.2 plus or minus 0.1 ng Ang1 per milliliter per hour, per hour, P less than 0.05). LBNP increased (P less than 0.05) pRA and pATII more in HiTol (9.9 plus or minus 2.2 ng Ang1 per milliliter per hour and 58 plus or minus 12 pg per milliliter) than LoTol (4.3 plus or minus 0.9 ng Angl per milliliter per hour and 28 plus or minus 6 pg per milliliter). In contrast, pVP was higher (P less than 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
20000109958
Acquisition Source
Ames Research Center
Document Type
Preprint (Draft being sent to journal)
Authors
Greenleaf, John E.
(NASA Ames Research Center Moffett Field, CA United States)
Petersen, T. W.
(Danish Aerospace Medical Center of Research Copenhagen, Denmark)
Gabrielsen, A.
(Danish Aerospace Medical Center of Research Copenhagen, Denmark)
Pump, B.
(Danish Aerospace Medical Center of Research Copenhagen, Denmark)
Bie, P.
(Danish Aerospace Medical Center of Research Copenhagen, Denmark)
Christensen, N.-J.
(Danish Aerospace Medical Center of Research Copenhagen, Denmark)
Warberg, J.
(Danish Aerospace Medical Center of Research Copenhagen, Denmark)
Videbaeck, R.
(Danish Aerospace Medical Center of Research Copenhagen, Denmark)
Simonson, S. R.
(Danish Aerospace Medical Center of Research Copenhagen, Denmark)
Norsk, P.
(Danish Aerospace Medical Center of Research Copenhagen, Denmark)
Dalton, Bonnie P.
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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