Mechanical activity of vascular smooth muscle under anoxia

Abstract

Under anoxia (N2 95%, CO2 5%) epinephrine (10-9-10- 5M), KCl (10-50 mM), and angiotensin (5 g/ml) caused a contraction in isolated aorta strips; however, when glucose was also absent, mechanical activity was almost completely abolished. Of various sugars (sucrose, galactose, fructose) and substrates (lactate, pyruvate) only glucose was capable of supporting contraction during anoxia. Inhibitors of glycolysis (iodoacetate 10-6 M and 2-deoxyglucose 10 mM) greatly diminished the response to epinephrine, KC1, and angiotensin under anoxic conditions with glucose present, but not under aerobic conditions. Furthermore, the intermediate metabolite of glycolysis such as glucose 6-phosphate could not be substituted for glucose under anaerobic conditions. Resting tension was not affected by anoxia without external glucose. The mechanical responses to epinephrine, KC1, and angiotensin may be supported by glycolysis during anoxia or by some other energy source under aerobic conditions when glycolysis was inhibited.