Release of adenosine from pig aortic endothelial cells during hypoxia and metabolic inhibition

The purpose of this study was to determine the effects of acute hypoxia on the ATP content of, and release of adenosine from, cultured endothelial cells. Pig aortic endothelial cells grown on plastic dishes or on microcarrier beads were incubated in physiological saline and gassed to achieve normoxia (media PO2 = 80-85 mmHg) or hypoxia (media PO2 = 2-12 mmHg) in the presence and absence of glucose and dipyridamole. Acute hypoxia did not significantly augment adenosine release from cells but did appear to decrease the reuptake of adenosine by cells. Hypoxia of a longer duration (3 h) led to ATP degradation and increased adenosine release when glucose was absent from the incubating medium, but not otherwise. Similarly, incubation of cells with NaCN in a glucose-free medium led to an increase in extracellular adenosine accumulation, whereas NaCN in the presence of glucose did not increase the accumulation of adenosine above the control level. The results suggest that the adenine nucleotide metabolism of cultured endothelial cells is not acutely sensitive to hypoxia or to inhibition of oxidative metabolism and can be maintained by glycolysis.