[Effects of L-arginine on pulmonary circulation and cerebral blood flow in acute and chronic hypoxic rats].

The effects of L-arginine (L-Arg) on pulmonary circulation and cerebral blood flow in acute and chronic hypoxic rats and their mechanism were studied. The results showed that bolus injection of L-Arg 400mg.kg-1 did not inhibit acute hypoxic pulmonary vasoconstriction (HPV), while 800mg.kg-1 could inhibit HPV. Neither of these two doses of L-Arg was found to have any influence on the change in cerebral blood flow during acute hypoxia. Long-term administration of L-Arg (300mg.kg-1/d) could attenuate chronic hypoxic pulmonary hypertension, the increase in pulmonary vascular resistance and right ventricular hypertrophy, and the HPV as well. It did not influence the cerebral blood flow. Since the inhibitor of NO synthetase, NG-nitro-L-arginine methyl ester, could antagonize the effect of L-Arg, it is suggested that an increase in the synthesis of NO might contribute to the effect of L-Arg.