The Role of Na⁺/H⁺ Exchange in Norepinephrine-induced Protein Synthesis in Neonatal Cultured Rat Cardiomyocytes : 53th Annual Scientific Session of the Japanese Circulation Society

Abstract

It is reported that Na⁺ influx contributes to stretch-induced cardiac hypertrophy. Na influx may also be involved in cardiac hypertrophy induced by catecholamine. In the present study, to test whether Na⁺/H⁺ exchange plays an important role in norepinephrine-induced cardiac hypertrophy, the effect of Na⁺/H⁺ exchange inhibitor, amiloride on protein systhesis was studied in cultured neonatal rat cardiomyocytes in serum free medium. [³H]Phenylalanine uptake was determined 24 and 48 hours after administration of norepinephrine with and without amiloride. In the control, norepinephrine increased [³H]phenylalanine uptake in a dose dependent manner (10^-5-10^-7 M). Prazosin (10^-7 M) and amiloride (10^-5-10^-4M) significantly attenuated the norepinephrine mediated protein synthesis. These results indicate that α₁-adrenergic stimulation enhances the protein synthesis through activation of Na⁺/H⁺ exchange. Therefore, Na⁺ influx and/or PH increase may play a key role in cardiac hypertrophy.