Effects of hypoxia on ET and NO levels in cultured umbilical venous endothelial cells of native Tibetan / 中国应用生理学杂志

<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>

Effects of ATP concentration and hypoxic exposure on RNA and protein synthesis activity in isolated mitochondria from rat brain / 生理学报

To explore the effects of ATP concentration in the medium and hypoxia exposure on mitochondrial DNA expression at transcriptional and translational level, rats were exposed to hypoxia in a hypobaric chamber simulating 4000 m above sea level for 3 d (acute hypoxia) or 40 d (chronic hypoxia). Cerebral cortex mitochondria were isolated from control and hypoxia-exposed rats by centrifugation program. The activities of intramitochondrial RNA and protein synthesis were measured respectively by the methods of incorporation of (3)H-UTP or (3)H-Leucine in a cell-free system in vitro in isolated organelle. The effect of different ATP concentrations in medium on incorporation activity of mitochondria from control rat brains was observed. The results showed that there was a 40% reduction in RNA synthesis and a 60% inhibition in protein synthesis in isolated mitochondria in vitro in acute hypoxia exposure compared to control. But in chronic hypoxic exposure, the inhibition of both RNA synthesis and protein synthesis was alleviated, being 72% and 76% of the normoxic control, respectively. Furthermore, the effect of ATP concentration in medium on mitochondrial RNA and protein synthesis in vitro showed two phases. The mitochondrial RNA and protein synthesis were inhibited when ATP concentration was either above or below 1 mmol/L in the incubation medium. These results indicate that hypoxia exposure affects the expression of mtDNA at both transcription and translation levels. It also suggests that the improvement of mitochondrial semi-automation during chronic hypoxic exposure may be at least one of the cellular mechanisms of body adaptation to hypoxia. The regulation of ATP in mitochondrial RNA and protein synthesis is therefore an economic and effective mode of regulation.