Premium
The effect of passive leg heating on alpha‐adrenergic mediated vasoconstriction in humans
Author(s) -
Keller David M,
Sander Mikael,
Crandall Craig G
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a563-b
Subject(s) - vasoconstriction , alpha (finance) , adrenergic , adrenergic receptor , alpha 2 adrenergic receptor , medicine , cardiology , surgery , receptor , construct validity , patient satisfaction
We tested the hypothesis that passive leg heating attenuates alpha‐adrenergic mediated vasoconstriction within the heated limb. Leg blood flow (LBF, ultrasound Doppler) and leg vascular conductance (LVC, LBF/mean arterial blood pressure) were measured during intra‐arterial infusion of the alpha 1 ‐selective agonist, phenylephrine (PE, 0.025 to 0.8 μg/kg/min) and the alpha 2 ‐selective agonist, BHT‐933 (1.0 to 10 μg/kg/min) during normothermia and passive heating of the assessed leg (via water perfused pant leg). Passive leg heating (~46 °C water temp) increased LVC from 4.4±0.5 to 13.7±1.7 ml/min/mmHg (P<0.05). Both PE and BHT‐933 reduced LVC more during leg heating vs normothermia (maximal decreases in LVC during heating vs normothermia: PE: 7.8±1.1 vs 2.8±0.5; BHT‐933: 8.7±1.8 vs 2.1±0.4 ml/min/mmHg; P<0.05 for both). However, the absolute LVC during the highest doses of the drugs were higher during passive leg heating compared to normothermia (LVC during heating vs normothermia: PE: 3.7±0.4 vs 2.0±0.3; BHT‐933: 3.8±0.2 vs 2.1±0.3 ml/min/mmHg; P<0.05 for both). Taken together these observations suggest that local heating does not decrease alpha‐adrenergic responsiveness but may counteract alpha‐adrenergic vasoconstriction and thereby decrease maximal sympathetic vasoconstriction. Project funded in part by the National Heart, Lung and Blood Institute (HL‐61388, HL‐84072, HL‐82426).