Oxygen-derived free radicals and local control of striated muscle blood flow

Abstract

The role of oxygen-derived free radicals in the local control of blood flow (BF) was evaluated in the microcirculation of the hamster cremaster muscle superfused with the enzymatic radical scavengers superoxide dismutase (SOD, 10 μg/ml) and catalase (CAT, 20 μg/ml). A bioassay of the cheek pouch microcirculation, using a previously described fluorescent microscopic technique, verified the in vivo activity of SOD and CAT. Increased superfusate O 2 content to 95% O 2 was correlated with an arteriolar vasoconstriction of approximately 50% and a 70% reduction in estimated BF, neither of which was affected by SOD-CAT treatment. These data suggest that free radicals do not mediate the vasoactive effect of O 2. SOD-CAT did not alter vascular reactivity because a twofold vasodilation and a fourfold BF increase after topical adenosine application and a fivefold vasoconstriction after topical norepinephrine were unaffected by enzyme treatment. A twofold vasodilation accompanied striated muscle contraction, but there was no effect of SOD-CAT. Assuming SOD and CAT are not excluded from the striated muscle interstitial space, we conclude that the release of superoxide radicals into the extracellular space does not participate in local microvascular control of cremaster muscle BF.