ABSTRACT
<p><b>AIM</b>To assay ET and NO in venous blood of native Tibetan and to investigate the effects of hypoxia on ET and NO levels in cultured umbilical venous endothelial cells of native Tibetan.</p><p><b>METHODS</b>ET and NO in venous blood of native Tibetan, immigrant Han and lowland Han were assayed. Umbilical venous endothelial cells (UVECs) from native Tibetan and immigrant Han newborns were cultured and divided into 4 groups: (1) Native Tibetan control group (TC), (2) Native Tibetan hypoxic group (TH), (3) Immigrant Han control group (HC), (4) Immigrant Han hypoxic group (HH). Supernatant was collected and ET and NO were detected.</p><p><b>RESULTS</b>Venous blood NO was significantly higher in native Tibetan than in immigrant Han, while ET lower in native Tibetan than in immigrant Han. ET excretion from UVECs was elevated while NO decreased in both Tibetan and Han groups after exposed to hypoxia. On time-points 12 h and 24 h, ET was significantly lower in TH than in HH, while concentration of NO showed no difference in TH and HH.</p><p><b>CONCLUSION</b>ET released by UVECs was higher in Han than in Tibetan after 12 h and 24 h hypoxic exposure, which may be in favor of lower vascular resistance and better fetal blood supply in Tibetan, and thus plays a role in the mechanisms of less intrauterine growth restriction (IUGR) throughout pregnancy and heavier birth weight of Tibetan newborns.</p>