Nitric oxide synthase inhibition by L-NAME prevents the decrease of Na+,K+-ATPase activity in midbrain of rats subjected to arginine administration

In the present study we investigated the effect of acute administration of L-arginine on Na+,K+-ATPase and Mg2+-ATPase activities and on some paramete rs of oxidative stress (chemiluminescence and total radical-trapping antiox idant parameter-TRAP) in midbrain of adult rats. We also tested the effect of L-NAME on the effects produced by arginine. Sixty-day-old rats were trea ted with an acute intraperitoneal injection of saline (group 1, control), a rginine (0.8 g/kg) (group II), L-NAME (2 mg/kg) (group III) or arginine (0. 8 g/kg) plus L-NAME (2 mg/kg) (group IV). Na+,K+-ATPase activity was signif icantly reduced in the arginine-treated rats, but was not affected by other treatments. In contrast, Mg2+-ATPase activity was not altered by any treat ment. Furthermore, chemiluminescence was significantly increased and TRAP w as significantly decreased in arginine-treated rats, whereas the simultaneo us injection of L-NAME prevented these effects. These results demonstrate t hat in vivo arginine administration reduces Na+,K+-ATPase activity possibly through free radical generation induced by NO formation.