Does amiloride reduce norepinephrine-induced protein synthesis in cultured neonatal rat cardiomyocytes?
Alpha 1-adrenergic stimulation enhances protein synthesis through activation of Na+/H+ exchange, suggesting Na+ influx and/or pH increase play a key role in cardiac hypertrophy.
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 synthesis was studied in cultured neonatal rat cardiomyocytes in serum free medium. 3HPhenylalanine uptake was determined 24 and 48 hours after administration of norepinephrine with and without amiloride. In the control, norepinephrine increased 3Hphenylalanine uptake in a dose dependent manner (10(-5)-10(-7) M). Prazosin (10(-7) M) and amiloride (10(-5)-10(-4) M) significantly attenuated the norepinephrine mediated protein synthesis. These results indicate that alpha 1-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.
Hori et al. (Mon,) studied this question.
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