VASCULAR OXIDATIVE-METABOLISM UNDER DIFFERENT METABOLIC CONDITIONS

Control of respiration in vascular smooth muscle was examined while the metabolic state of the tissue was manipulated. During KCl-induced contractures in the presence of 5 mM glucose, oxygen consumption increased by 10 nmol / per min g without any decrease in phosphocreatine (PCr) or ATP as determined by P-31-NMR indicating a control of respiration which does not involve changes in high-energy phosphates (e.g., ADP, phosphorylation potential). However, when aortae with resting tone in the absence of substrate were then provided with 5 mM 2-deoxyglucose as the sole substrate, oxygen consumption increased 7.4 nmol / min per g while PCr decreased by more than 50% (resulting in a 2-fold increase in the calculated free ADP) with no change in tension from resting tone. During a subsequent KCI induced contracture in the presence of 2-deoxyglucose, oxygen consumption increased an additional 7.2 nmol / min per g while PCr continued to decline. Therefore, at least two mechanisms of respiratory control may exist in sheep aorta, one dependent and the other independent of changes in high-energy phosphates.