During dynamic exercise in the heat, increases in skin blood flow are attenuated in hypertensive subjects when compared with normotensive subjects. We studied responses to passive heat stress (water-perfused suits) in eight hypertensive and eight normotensive subjects, Forearm blood flow was measured by venous-occlusion plethysmography, mean arterial pressure (MAP) was measured by Finapres, and forearm vascular conductance (FVC) was calculated. Bretylium tosylate (BT) iontophoresis was used to block active vasoconstriction in a small area of skin. Skin blood flow was indexed by laser-Doppler flowmetry at BT-treated and untreated sites, and cutaneous vascular conductance was calculated. In normothermia, FVC was lower in hypertensive than in normotensive subjects (P < 0.01). During heat stress, FVC rose to similar levels in both groups (P > 0.80); concurrent cutaneous vascular conductance increases were unaffected by BT treatment (P > 0.60). MAP was greater in hypertensive than in normotensive subjects during normothermia (P < 0.05, hypertensive vs. normotensive subjects). During hyperthermia, MAP fell in hypertensive subjects but showed no statistically significant change in normotensive subjects (P < 0.05, hypertensive vs. normotensive subjects). The internal temperature at which vasodilation began did not differ between groups (P > 0.80). FVC is reduced during normothermia in unmedicated hypertensive subjects; however, they respond to passive heat stress in a fashion no different from normotensive subjects.
|Original language||English (US)|
|Number of pages||6|
|Journal||Journal of applied physiology|
|Publication status||Published - Jul 1 1998|
- Laser-Doppler flowmetry
ASJC Scopus subject areas
- Physiology (medical)