Effects of exogenous and endogenous norepinephrine on the oxygen availability of intact muscular arteries

A Polarographic technique was used to evaluate changes in arterial wall oxygen availability during systemically administered and endogenously released norepinephrine. A 125-μ, diameter bare-tipped platinum electrode was advanced into the media of exposed femoral arteries in 23 anesthetized dogs. Tissue oxygen availability was recorded in terms of current flow through the Polarographic electrode system. Intravenously administered norepinephrine produced a vasopressor response and was associated with significant reductions in the oxygen current in intact and autografted vessels. Similar reductions in intramural oxygen availability were produced by ipsilateral lumbar sympathetic ganglia stimulation. The norepinephrine-induced changes in oxygen availability were produced even when the blood pressure in the femoral artery was held constant by pump perfusion. Furthermore, intramural oxygen availability could not be reduced by passive increases in luminal pressure. These findings indicate that norepinephrine reduced intramural oxygen availability by a direct metabolic effect on the smooth muscle of the vessel wall.