title: The role of Na+/H+ exchange in norepinephrine-induced protein synthesis in neonatal cultured rat cardiomyocytes.
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 synthesis 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(-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.
authors.affiliation: First Department of Medicine, Osaka University Medical School, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Hori
authors.forename: N
authors.initials: N
authors.lastname: Nakatsubo
authors.forename: T
authors.initials: T
authors.lastname: Kagiya
authors.forename: K
authors.initials: K
authors.lastname: Iwai
authors.forename: H
authors.initials: H
authors.lastname: Sato
authors.forename: K
authors.initials: K
authors.lastname: Iwakura
authors.forename: A
authors.initials: A
authors.lastname: Kitabatake
authors.forename: T
authors.initials: T
authors.lastname: Kamada
mesh_terms: D000584:Amiloride / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D000831:Animals, Newborn; D006332:Cardiomegaly / Q000209:etiology / Q000378:metabolism; D002478:Cells, Cultured; D007474:Ion Exchange; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D009638:Norepinephrine / Q000009:adverse effects* / Q000037:antagonists & inhibitors; D011224:Prazosin / Q000494:pharmacology; D014176:Protein Biosynthesis; D011522:Protons; D051381:Rats; D012964:Sodium / Q000378:metabolism / Q000502:physiology*
chemical_list: D011522:Protons; D000584:Amiloride; D012964:Sodium; D009638:Norepinephrine; D011224:Prazosin