Bioenergetic alterations in cultivated pulmonary artery and aortic endothelial cells exposed to normoxia and hypoxia.

Endothelial cells function under conditions of different oxygen availability under physiologic conditions and a variety of pathologic states. We determined the effect of normal and low O2 tensions on three key bioenergetic enzymes [pyruvate kinase (ATP:pyruvate phosphotransferase, EC 2.7.1.40), phosphofructokinase (ATP:D-fructose-6-phosphate 1-phosphotransferase, EC 27.1.11) and cytochrome aa3] in culture-maintained endothelial cells derived from calf pulmonary artery and aorta. Endothelial cells derived from pulmonary artery and aorta demonstrate similar bioenergetic enzyme activities when exposed to the same PO2 in vitro. Endothelial cells exposed to hypoxia in vitro for 48-96 hr show significantly increase activities of 2 key glycolytic enzymes: pyruvate kinase, and phosphofructokinase. Freshly isolated intimal strips from calf pulmonary artery (normal PO2 = 40 torr) show significantly greater activities of PyKi than aortic intimal strips (normal PO2 = 90 torr), suggesting that a similar pattern occurs in vivo. The data suggest that both cell types have a common bioenergetic pattern which is genetically determined and that this pattern is modified by regulatory mechanisms geared to ambient O2 tension. As endothelial cells of both types are not uncommonly exposed to hypoxic conditions, these regulatory mechanisms may play an important role in maintaining vascular integrity.