PurposeTo study the changes of serum nitric oxide(NO)and endothelin(ET)levels by L-Arg therapy in acute hypoxic model. MethodsNADPH diaphorase histochemical staining method, Griess biochemical assay and radioimmune assay were applied to investigate the changes of nitric oxide synthase (NOS) ,NO, cGMP and ET in normal, hypoxic and L-Arg treated hypoxic rats. Resultsduring acute hypoxia, while serum ET rose up significantly, both the levels of serum NO and cGMP and the activity of NOS were significantly lower. After the application of L-Arg therapy, the activity of NOS did not change significantly, but the levels of serum NO and cGMP rose up significantly, and the level of serum ET was to the opposite direction. ConclusionsNO and ET may modulate hypoxic pulmonary hypertension, and acute hypoxia can result in acute hypoxic pulmonary hypertension. L-Arg can reverse the acute hypoxic hypertension.

Objective　To investigate the protective effects of mild hypothermia and/or felbamate on hypoxic-ischemic (HI) brain damage. Methods　 The HI model rats (subjected to unilateral right carotid artery ligation and given 8% oxygen for 2 h) were allocated to mild hypothermia groups （the brain temperature dropped by 4.5℃) for 24 h course (Hy24，n=26) and 72 h course (Hy72, n=48) , felbamate group (Fbm, n=48), Hy24 combined with Fbm group (HF, n=51) and placebo group (Pla, n=48). The control group (Con, n=42) was shame-operated animals. The rectal temperature (RT) and brain temperature (BT) of experimental animals were monitored. The plasma S-100 and CK-BB levels, brain injury scores (BIS) and percentage of hippocampal dead neurons (HDNP) and the behavioral test of Morris Water Maze were used to assess the protective effects. Results　BT was 0.3～0.6℃ which was lower than RT (r=0.99, P＜0.01). RT dropped by 4～5℃in Hy24, Hy72 and HF groups. RT maintained in 36～37℃in Fbm and Pla groups. The peak levels of plasma S-100 and CK-BB in Pla group (1.21～1.24 μg/L and 52.9～54.2 IU/L, respectively) were about 2 to 3 times as high as normal levels between 24 h to 48 h after HI, while the plasma S-100 and CK-BB levels in Hy24，Hy72, Fbm and HF groups were lower than Pla group (P＜0.01). At 72 h, 14d and 60d after HI, the reductions, of BIS and HDNP in Hy72 group were 58%, 85% and 87%, HF group 56%, 77% and 76%, Hy24 group 35%, 58% and 47% and Fbm group 35%, 66% and 67%, respectively. The order of spatial remember function was Con, and HF>Hy72>Hy24≥Fbm>Pla. Conclusions　 Mild hypothermia and/or felbamate showed different protective effects on brain HI damage as reflected by the changes of the plasma S-100 and CK-BB levels, the results of behavior assessment and histopathological changes. The optimal effect was obtained when hypothermia and felbamate were used simultaneously.