Effect of L-Arginine on Na+,K+-ATPase Activity in Rat Aorta Endothelium

The effect of L-arginine on the Na+,K+-ATPase activity in rat aorta endothelium was studied at its physiological concentrations in the range of 10–6-10–3 M. The enzyme activity was 35.5% increased by low concentrations of L-arginine (≤10–5 M) and its activity was 32.3-37.1% decreased at the L-arginine concentrations of 10–4-10–3 M. A similar inhibition (by 34.5-42.8%) was also found in the presence of a NO-donor nitroglycerol (10–4-10–3 M). An optical isomer of L-arginine, D-arginine, at the concentrations of ≤10–5 M also increased the enzyme activity by 37.1%, but its inhibiting effect was much less pronounced and was 15.7% at the D-arginine concentration of 10–3 M. An inhibitor of NO-synthase, L-NAME (NG-nitroarginine, methyl ester), failed to inhibit Na+,K+-ATPase. However, the presence of L-NAME abolished the inhibition of Na+,K+-ATPase by high concentrations of L-arginine. Thus, the effect of L-arginine on the endothelial Na+-pump depended on its concentration, and it is suggested that the enzyme inhibition by high concentrations of L-arginine should be associated with activation of the endogenous synthesis of NO.