Objective: To investigate the effects of the N omega-nitro-L-arginine methyl ester (L-NAME) on pulmonary artery of rats during 14 days simulated weightlessness.
Methods: Sixteen male Wistar rats were randomly divided into control group and tail-suspension (TP) group (each n=8). Vascular bathing technique was used to measure the contractile responses of rats pulmonary artery rings to phenylephrine (PE), dilatory responses to acetylcholine (Ach) and contractile response to PE in presence of L-NAME. Nitric oxide (NO) content in pulmonary tissues was determined using nitrate enzyme reduction method.
Results: After simulated weightlessness for 14 days,the contractile response of rat pulmonary artery to PE (1x10(-5)-1x10(-7) mol/L) decreased significantly (all P<0.01); the dilatory response to Ach (1x10(-6)-1x10(-8) mol/L) increased significantly (all P<0.05). L-NAME abolished the differential responses to PE in TS and control groups, had no significant differences compared with control group, and NO content was also significantly increased. There were significant differences between the two groups (P<0.05).
Conclusion: Larger amount of NO is released in vascular endothelium after 14 days TS, which might partly explain the decrease in the contractile responses of pulmonary artery.