ABSTRACT
<p><b>AIM</b>To investigate changes of VEC and CEC under acute hypoxia.</p><p><b>METHODS</b>Observe CEC in blood under acute hypoxia morphologically and count the number of CEC by optical microscope, measure LDH activity of young CEC and VEC by histochemical staining image analysis.</p><p><b>RESULTS</b>LDH activities of VEC in hypoxic groups are lower than that in the group before hypoxia and decrease progressively with hypoxia time. LDH activities of young CEC in groups after hypoxia and before hypoxia are the same and are apparently lower than that of VEC. Before hypoxia most of CEC are aging, the number of CEC from hypoxic groups is greater than that before hypoxia and increases progressively with hypoxia time and most of CEC from hypoxic groups are young.</p><p><b>CONCLUSION</b>The morphology and number of CEC may reflect the extent to which the vascular is injured. LDH activity of VEC may reflect the transformation from VEC into CEC. LDH activity of young CEC may reflect the extent to which the VEC is injured when falling from vascular wall.</p>