Substrate supply and function of isolated venous smooth muscle under anoxia and metabolic inhibition.

The contractile recoverability of isolated portal veins made hypodynamic by removal of glucose from the perfusion medium by diverse exogenous substrates was studied. It was found that glucose, mannose, pyruvate, lactate, acetate, and butyrate readily restored contraction. The effects of anoxia and metabolic inhibitors were also investigated. Both anoxia and dinitrophenol abolished spontaneous activity within 10 min. Fluoroacetate markedly depressed contractility (-60.9 +/- 2.8% at 10 min), the reduction being essentially similar in medium with or without glucose. 2-Deoxy-D-glucose (2-DG) in glucose medium reduced contractility only slightly whereas in the absence of glucose it drastically inhibited contraction (-76% at 10 min and -97% at 40 min). Intracellular ATP was significantly reduced by anoxia and fluoroacetate in medium with or without glucose and by 2-DG only in substrate-free medium. However, ATP depletion showed no clear correlation with the extent of contractile depression. These findings indicate a strong dependence for mechanical activity in this vein on aerobic metabolic pathways. But, from the results with 2-DG, it is suggested that an adequate glucose metabolism might be of importance for functional processes other than contraction itself.