RESUMO
OBJECTIVE: To explore the mitochondrial mechanism of adaptation to hypoxia of Tibetan. METHODS: The body weights and heights of 32 neonates borne by native Tibetan women and of 20 neonates borne by immigrant Han women were measured immediately after birth. The placentae were collected to measure the weight and volume and placental mitochondria were isolated. The mitochondrial respiratory state III (ST3), respiratory state IV (ST4), and respiratory control ratio (RCR) were measured with Clark electrode and the oxidative phosphorylation rate (OPR) was calculated. RESULTS: (1) The mean body weight of the neonates borne by native Tibetan women was 3.495+/-0.493 kg, significantly greater than that of the neonates borne by immigrant Han women (2.952+/-0.388 kg, t=3.365, P=0.000). The mean body height of the neonates borne by native Tibetan women was 49.81+/-2.56 cm, significantly greater than that of the neonates borne by immigrant Han women (48.10+/-2.30 cm, t=2.025, P=0.000). The mean weight of the placentae of the native Tibetan women was 0.509+/-0.090 kg, significantly greater than that of the migrant Han women too (0.429+/-0.099 kg, t=0.695, P=0.004), and the mean volume of the placentae of the native Tibetan women was 657.66+/-167.10 cm3, significantly greater than that of the migrant Han women (500.46+/-140.69 cm3, t=1.834, P=0.001). (2) The ST3, RCR, and OPR of the placental mitochondria of the native Tibetan women were 4.22+/-0.97, 67.78+/-13.57 nmol Oxmin(-1)xmg pro(-1), and 117.93+/-32.69 nmol Oxmin(-1)xmg pro(-1), all significantly higher than those of the migrant Han women (3.21+/-0.37, 41.27+/-10.49 nmol Oxmin(-1)xmg pro(-1), and 68.94+/-28.88 nmol Oxmin(-1)xmg pro(-1) respectively, t=3.232, 5.257, and 2.985, P=0.004, 0.000, and 0.001 respectively), while ST4 showed no significant difference between the two groups (16.58+/-3.53 nmol Oxmin(-1)xmg pro(-1) vs. 14.79+/-4.69 nmol Oxmin(-1)xmg pro(-1), t=1.069, P=0.297). CONCLUSION: The mitochondrial oxidative phosphorylation activity is significantly higher in the native Tibetan than in the immigrant Han population, indicating that Tibetans are able to utilize much more oxygen under hypoxic conditions at high altitude. This may be an important mechanism by which Tibetans adapt well to hypoxic environment at high altitude.