Regulation of human skeletal muscle perfusion and its heterogeneity during exercise in moderate hypoxia

TY - JOUR

T1 - Regulation of human skeletal muscle perfusion and its heterogeneity during exercise in moderate hypoxia

AU - Heinonen, Ilkka H

AU - Kemppainen, Jukka

AU - Kaskinoro, Kimmo

AU - Peltonen, Juha E

AU - Borra, Ronald

AU - Lindroos, Markus

AU - Oikonen, Vesa

AU - Nuutila, Pirjo

AU - Knuuti, Juhani

AU - Boushel, Robert Christopher

AU - Kalliokoski, Kari K

PY - 2010/7/1

Y1 - 2010/7/1

N2 - Although many effects of both acute and chronic hypoxia on the circulation are well characterized, the distribution and regulation of blood flow (BF) heterogeneity in skeletal muscle during systemic hypoxia is not well understood in humans. We measured muscle BF within the thigh muscles of nine healthy young men using positron emission tomography during one-leg dynamic knee extension exercise in normoxia and moderate physiological systemic hypoxia (14% O 2 corresponding to ∼3,400 m of altitude) without and with local adenosine receptor inhibition with femoral artery infusion of aminophylline. Systemic hypoxia reduced oxygen extraction of the limb but increased muscle BF, and this flow increment was confined solely to the exercising quadriceps femoris muscle. Exercising muscle BF heterogeneity was reduced from rest (P = 0.055) but was not affected by hypoxia. Adenosine receptor inhibition had no effect on capillary BF during exercise in either normoxia or hypoxia. Finally, one-leg exercise increased muscle BF heterogeneity both in the resting posterior hamstring part of the exercising leg and in the resting contralateral leg, whereas mean BF was unchanged. In conclusion, the results show that increased BF during one-leg exercise in moderate hypoxia is confined only to the contracting muscles, and the working muscle hyperemia appears not to be directly mediated by adenosine. Increased flow heterogeneity in noncontracting muscles likely reflects sympathetic nervous constraints to curtail BF increments in areas other than working skeletal muscles, but this effect is not potentiated in moderate systemic hypoxia during small muscle mass exercise.

AB - Although many effects of both acute and chronic hypoxia on the circulation are well characterized, the distribution and regulation of blood flow (BF) heterogeneity in skeletal muscle during systemic hypoxia is not well understood in humans. We measured muscle BF within the thigh muscles of nine healthy young men using positron emission tomography during one-leg dynamic knee extension exercise in normoxia and moderate physiological systemic hypoxia (14% O 2 corresponding to ∼3,400 m of altitude) without and with local adenosine receptor inhibition with femoral artery infusion of aminophylline. Systemic hypoxia reduced oxygen extraction of the limb but increased muscle BF, and this flow increment was confined solely to the exercising quadriceps femoris muscle. Exercising muscle BF heterogeneity was reduced from rest (P = 0.055) but was not affected by hypoxia. Adenosine receptor inhibition had no effect on capillary BF during exercise in either normoxia or hypoxia. Finally, one-leg exercise increased muscle BF heterogeneity both in the resting posterior hamstring part of the exercising leg and in the resting contralateral leg, whereas mean BF was unchanged. In conclusion, the results show that increased BF during one-leg exercise in moderate hypoxia is confined only to the contracting muscles, and the working muscle hyperemia appears not to be directly mediated by adenosine. Increased flow heterogeneity in noncontracting muscles likely reflects sympathetic nervous constraints to curtail BF increments in areas other than working skeletal muscles, but this effect is not potentiated in moderate systemic hypoxia during small muscle mass exercise.

KW - Adenosine

KW - Adult

KW - Altitude

KW - Anoxia

KW - Capillaries

KW - Exercise

KW - Hemodynamics

KW - Humans

KW - Hyperemia

KW - Leg

KW - Male

KW - Muscle Contraction

KW - Muscle, Skeletal

KW - Oxygen

KW - Perfusion

KW - Quadriceps Muscle

KW - Receptors, Purinergic P1

KW - Rest

KW - Sympathetic Nervous System

U2 - 10.1152/ajpregu.00056.2010

DO - 10.1152/ajpregu.00056.2010

M3 - Journal article

C2 - 20427728

SN - 0363-6119

VL - 299

SP - R72-9

JO - American Journal of Physiology - Regulatory Integrative and Comparative Physiology

JF - American Journal of Physiology - Regulatory Integrative and Comparative Physiology

IS - 1

ER -