Evidence that oxidative stress is involved in the inhibitory effect of proline on Na+,K+-ATPase activity in synaptic plasma membrane of rat hippocampus

In the present study, we investigated the effect of Vitamins E and C on the inhibition of Na+,K+-ATPase activity provoked by proline (Pro) administration in rat hippocampus. Five-day-old rats were pretreated for 1 week with daily i.p. administration of saline (control) or Vitamin E (40 mg/kg) and Vitamin C (100 mg/kg). Twelve hours after the last injection, animals received one single injection of Pro (12.8 mumol/g of body weight) or saline and were killed 1 h later. Results showed that Na+,K+-ATPase activity was decreased in the Pro-treated rats and that the pretreatment with Vitamins E and C prevented this effect. In another set of experiments, we investigated the in vitro effect of 1.0 mM Pro on Na+,K+-ATPase activity from synaptic membranes of hippocampus of rats. Pro significantly inhibited (30%) Na+,K+-ATPase activity. We also evaluated the effect of preincubating glutathione, trolox and N-pi -nitro-L-arginine methyl ester (L-NAME) alone or combined with Pro on Na+,K+-ATPase activity. Tested drugs did not alter Na+,K+-ATPase activity, but glutathione prevented the inhibitory effect of Pro on this enzyme activity. These results suggest that the in vivo and in vitro inhibitory effect of Pro on Na+,K+-ATPase activity is probably mediated by free radicals that may be involved in the neurological dysfunction found in hyperprolinemic patients. (C) 2003 ISDN. Published by Elsevier Ltd. All rights reserved.