Effects of reduced temperature on capillary flow and reactive hyperemia in red and white skeletal muscle

Abstract

Tissue temperature was reduced 10° below normal body temperature in the red anterior (ALD) and white posterior latissimus dorsi (PLD) muscles of the chicken. Temperature reduction for a 13-min period resulted in biphasic changes in ALD capillary velocity. Three minutes after temperature was decreased velocity was reduced to 33% of control. Ten minutes later, velocity had risen to 48% of control. Steady-state capillary velocities (measured 0.5 to 3 hr after temperature reduction) were reduced by 25% in the ALD and by 41% in the PLD. Reactive hyperemia peak velocity was unchanged in the ALD but was significantly reduced in the PLD. The duration of reactive hyperemia following 60-sec occlusions decreased by 52% in the ALD and by 43% in the PLD at low temperature. Excess flow decreased by 71% in both muscles following 60-sec occlusions at reduced temperature. Comparable reductions in percentage flow debt repayment occurred in both muscles. Therefore, temperature reduction decreased control capillary red cell velocity, hyperemia duration, excess flow, and percentage flow debt repayment following 60-sec occlusions; the changes were comparable in both red and white muscles. The reduced duration of reactive hyperemia at low temperature may be due to a decrease in vasodilator metabolite production during ischemia. The absence of a comparable effect on peak flow suggests that vascular sensitivity may be greater at low temperature.