Local temperature-sensitive mechanisms are important mediators of limb tissue hyperemia in the heat-stressed human at rest and during small muscle mass exercise

TY - JOUR

T1 - Local temperature-sensitive mechanisms are important mediators of limb tissue hyperemia in the heat-stressed human at rest and during small muscle mass exercise

AU - Chiesa, Scott T

AU - Trangmar, Steven J

AU - Kalsi, Kameljit K

AU - Rakobowchuk, Mark

AU - Banker, Devendar S

AU - Lotlikar, Makrand D

AU - Ali, Leena

AU - González-Alonso, José

N1 - Copyright © 2015 the American Physiological Society.

PY - 2015/7/15

Y1 - 2015/7/15

N2 - Limb tissue and systemic blood flow increases with heat stress, but the underlying mechanisms remain poorly understood. Here, we tested the hypothesis that heat stress-induced increases in limb tissue perfusion are primarily mediated by local temperature-sensitive mechanisms. Leg and systemic temperatures and hemodynamics were measured at rest and during incremental single-legged knee extensor exercise in 15 males exposed to 1 h of either systemic passive heat-stress with simultaneous cooling of a single leg (n = 8) or isolated leg heating or cooling (n = 7). Systemic heat stress increased core, skin and heated leg blood temperatures (Tb), cardiac output, and heated leg blood flow (LBF; 0.6 ± 0.1 l/min; P < 0.05). In the cooled leg, however, LBF remained unchanged throughout (P > 0.05). Increased heated leg deep tissue blood flow was closely related to Tb (R(2) = 0.50; P < 0.01), which is partly attributed to increases in tissue V̇O2 (R(2) = 0.55; P < 0.01) accompanying elevations in total leg glucose uptake (P < 0.05). During isolated limb heating and cooling, LBFs were equivalent to those found during systemic heat stress (P > 0.05), despite unchanged systemic temperatures and hemodynamics. During incremental exercise, heated LBF was consistently maintained ∼ 0.6 l/min higher than that in the cooled leg (P < 0.01), with LBF and vascular conductance in both legs showing a strong correlation with their respective local Tb (R(2) = 0.85 and 0.95, P < 0.05). We conclude that local temperature-sensitive mechanisms are important mediators in limb tissue perfusion regulation both at rest and during small-muscle mass exercise in hyperthermic humans.

AB - Limb tissue and systemic blood flow increases with heat stress, but the underlying mechanisms remain poorly understood. Here, we tested the hypothesis that heat stress-induced increases in limb tissue perfusion are primarily mediated by local temperature-sensitive mechanisms. Leg and systemic temperatures and hemodynamics were measured at rest and during incremental single-legged knee extensor exercise in 15 males exposed to 1 h of either systemic passive heat-stress with simultaneous cooling of a single leg (n = 8) or isolated leg heating or cooling (n = 7). Systemic heat stress increased core, skin and heated leg blood temperatures (Tb), cardiac output, and heated leg blood flow (LBF; 0.6 ± 0.1 l/min; P < 0.05). In the cooled leg, however, LBF remained unchanged throughout (P > 0.05). Increased heated leg deep tissue blood flow was closely related to Tb (R(2) = 0.50; P < 0.01), which is partly attributed to increases in tissue V̇O2 (R(2) = 0.55; P < 0.01) accompanying elevations in total leg glucose uptake (P < 0.05). During isolated limb heating and cooling, LBFs were equivalent to those found during systemic heat stress (P > 0.05), despite unchanged systemic temperatures and hemodynamics. During incremental exercise, heated LBF was consistently maintained ∼ 0.6 l/min higher than that in the cooled leg (P < 0.01), with LBF and vascular conductance in both legs showing a strong correlation with their respective local Tb (R(2) = 0.85 and 0.95, P < 0.05). We conclude that local temperature-sensitive mechanisms are important mediators in limb tissue perfusion regulation both at rest and during small-muscle mass exercise in hyperthermic humans.

KW - Adult

KW - Blood Flow Velocity

KW - Body Temperature Regulation

KW - Heat Stress Disorders

KW - Hemodynamics

KW - Humans

KW - Hyperemia

KW - Male

KW - Muscle Contraction

KW - Muscle, Skeletal

KW - Regional Blood Flow

KW - Thermosensing

KW - Time Factors

KW - Young Adult

U2 - 10.1152/ajpheart.00078.2015

DO - 10.1152/ajpheart.00078.2015

M3 - Article

C2 - 25934093

SN - 0363-6135

VL - 309

SP - H369-H380

JO - AJP - Heart and Circulatory Physiology

JF - AJP - Heart and Circulatory Physiology

IS - 2

ER -