Metabolic factors from exercising muscle and the proliferation of endothelial cells

In order to identify factors that may be involved in angiogenesis in mammalian skeletal muscle after endurance exercise, the growth of cultured vascular endothelial cells derived from the canine hindlimb was measured in response to hypoxia and changes in temperature and concentrations of hydrogen ion and adenosine. Endothelial cells were freed from vessels of exsanguinated canine hindlimbs using collagenase. Cultures were grown on plastic culture dishes at 37 degrees C and 40 torr CO2 in air. Primary cultures reached confluency by 21 days. Cell number in secondary cultures was significantly increased in 7 days by exposure to 35 torr oxygen for 1 h daily, but cell growth rate was unaffected by 65 torr oxygen. Cell growth was inhibited when hydrogen ion concentration was increased by adding lactic acid daily (5 mmol X l-1). Exposing cell cultures for 1 h daily to an elevated PCO2 (70 torr) or to an environmental temperature of 41 degrees C, adding sodium lactate (5 mmol X l-1), or adenosine (10 or 100 mumol X l-1) daily did not affect cell growth rate. Thus, hypoxia increased the growth rate of cultured vascular endothelial cells and may play a role in blood vessel growth in vivo.