Biochemical alterations caused by hypoxia in the isolated rabbit aorta. Correlation with changes in arterial contractility

A graded reduction in the oxygen tension of the medium bathing aortic strips resulted in a decrease in creatine phosphate and adenosine triphosphate levels in the tissue, but only the fall in creatine phosphate could be correlated with the contractile changes observed during hypoxia. The tissue glycogen concentration was not altered at any oxygen tension, indicating that under the conditions of the experiment glycogenolysis did not contribute substrate in significant amounts. Although lactate concentrations rose as the oxygen tension was progressively lowered, changes in the concentration of this metabolite did not correlate with the contractile response to hypoxia. The reduction in contractile tone induced by lowering oxygen tension of the medium was less when the tissue was exposed to 25 mM glucose than it was with 5 mM glucose. Addition of pyruvate did not mimic this sparing effect of glucose. These results indicate that the loss of contractile tone in arterial muscle exposed to low oxygen tensions is not directly attributable to a deficit in the availability of adenosine triphosphate within the tissue but, rather, is a consequence of more subtle alterations in the energy metabolism of the muscle.