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Decreased active vasodilator sensitivity in aged skin
W L Kenney1, A L Morgan, W B Farquhar
1Noll Physiological Research Center, Pennsylvania State University, University Park 16802-6900, USA.
The American Journal of Physiology
|April 1, 1997
Summary
Older adults show reduced skin blood flow during heat stress due to impaired vasodilation, not increased vasoconstriction. This limits their ability to cool effectively during exercise.
Area of Science:
- Physiology
- Thermoregulation
- Aging Research
Background:
- Older adults exhibit an attenuated increase in cutaneous vascular conductance (CVC) when exposed to heat stress.
- The role of noradrenergic vasoconstriction in this age-related blunted CVC response is not fully understood.
Purpose of the Study:
- To investigate the hypothesis that augmented or sustained noradrenergic vasoconstriction contributes to the age-related difference in CVC during heat stress.
- To compare the cutaneous vascular response to exertional heat stress in young and older men.
Main Methods:
- Fifteen young and 15 older men exercised in a 36°C environment.
- Skin perfusion was measured using laser-Doppler flowmetry at a control site and a site pretreated with bretylium tosylate (BT) to block norepinephrine release.
- Cutaneous vascular conductance (CVC) was expressed as a percentage of maximal CVC (%CVCmax).
Main Results:
- Neither age nor BT affected the maximal CVC achieved at high core temperatures.
- The rise in CVC in response to increasing esophageal temperature was shifted to the right in older men at both control and BT sites.
- Forearm vascular conductance (FVC) was 40-50% lower in older men during exercise, indicating reduced skin blood flow.
Conclusions:
- The age-related attenuation in CVC during exertional heat stress is not mediated by increased noradrenergic vasoconstriction.
- Decreased active vasodilator sensitivity and potential structural limitations to vasodilation contribute to impaired heat loss in older adults.