Observations on the Role of Diminished Oxygen Tension in the Functional Hyperemia of Skeletal Muscle

Abstract

The hypothesis that lowered tissue oxygen tension acting on vascular smooth muscle can explain functional hyperemia in skeletal muscle was examined in ten dogs. A comparison was made between the blood flow increment that accompanied rapid, rhythmic contraction of a gastrocnemius muscle and the flow change that occurred in the same muscle at rest during its perfusion with venous blood obtained from the resting or contracting gastrocnemius muscle of the opposite leg. Blood P O O2 , pH, and P CO CO2 were measured in samples of venous blood from the muscle. There was no evidence that the perfusion circuit traumatized the perfused blood. During functional hyperemia, the increases in blood flow averaged 173%, and the average venous P O O2 , was 25 mm Hg. During venous perfusion, the maximum increases in blood flow averaged 56%, and the average venous P O O2 , was 23 mm Hg. When the muscle was stimulated to contract during its perfusion with venous blood, increases in blood flow occurred which averaged 143%, despite additional falls in venous blood P O O2 that averaged only 3 mm Hg. These studies suggest that the effect of lowered P O O2 on vascular smooth muscle does not produce sufficient vasodilatation to explain functional hyperemia in skeletal muscle.

Local and reflex factors affecting the distribution of the peripheral blood flow during arterial hypoxia in the rabbit

“…The absence of an obvious dilator respouse in the muscle bed of 'de-efferented' animals is at variance with the findings in 'de-afferented' animals, with estimates of the local effects of hypoxia in perfusion studies (Crawford et al 1959;Haddy & Scott, 1964, Ross et al 1964Haddy, 1966), and with results in the denervated limb of intact animals (Chalmers et al 1966). Incomplete block has been excluded in 'de-efferented' animals (Chalmers et al 1967 c), and the production of other constrictor substances during hypoxia in amounts sufficient to account for the findings seems improbable.…”

Effects of Local and General Hypoxia on Iliac Flow

“…Vasodilation due to arterial hypoxia does not reach these extreme levels [38]. Nevertheless, a specific upper limit exists under given conditions when only one parameter is changed.…”

“…It is well known that local oxygen lack produces marked vasodilation in skeletal muscle vessels [6,18,21,24,34,36,37,38]. Although there is less agreement on the action of increased CO, content or decreased pH of the perfusing blood on skeletal muscle vessel tone, the available evidence appears to indicate that lowering the pH locally produces, in most instances, an increase in arterial blood flow [17,28,44,45].…”

Time Course of Vascular Resistance and Venous Oxygen Changes following Brief Tetanus of Dog Skeletal Muscle

“…There is strong evidence supporting a role for at least three factors in the production of metabolic vasodilation. These factors are the potassium ion (27), osmolarity (28), and a substance related to oxidative metabolism (29,30). The concept that two or more factors are involved in the control of vascular resistance during active hyperemia has received considerable experimental support.…”