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1 Department of Physical Education, Exercise and Sports Sciences, East Tennessee State University, Johnson City, Tennessee, United States
2 Medicine, West Virginia University, Morgantown, West Virginia, United States
3 Division of Exercise Physiology, West Virginia Univ Sch Med, Morgantown, West Virginia, United States
* To whom correspondence should be addressed. E-mail: mdelp{at}hsc.wvu.edu.
The purpose of this investigation was to determine mean arterial pressure (MAP) and regional vascular conductance response in young and old Fisher-344 rats during orthostatic stress, i.e., 70° head-up tilt (HUT). Both groups demonstrated directionally different changes in MAP during HUT (young, 7% increase; aged, 7% decrease). Vascular conductance during HUT in young rats decreased in most tissues, but largely remained unchanged in the old animals. Based upon the higher vascular conductance of white adipose tissue from old rats during HUT, resistance arteries from white visceral fat were isolated and studied in vitro. There was diminished maximal vasoconstriction to phenylephrine and norepinephrine (NE: young, 42 ± 5 %; aged, 18 ± 6 % vasoconstriction) in adipose resistance arteries from aged rats. These results demonstrate that aging reduces the ability to maintain MAP during orthostatic stress, and this is associated with a diminished vasoconstriction of adipose resistance arteries.
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