title: Endothelin-1 induced hypertrophic effect in neonatal rat cardiomyocytes: involvement of Na+/H+ and Na+/Ca2+ exchangers.
abstract: Endothelin-1 (ET-1) is a potent agonist of cell growth that also stimulates Na(+)/H(+) exchanger isoform 1 (NHE-1) activity. It was hypothesized that the increase in intracellular Na(+) ([Na(+)](i)) mediated by NHE-1 activity may induce the reverse mode of Na(+)/Ca(2+) exchanger (NCX(rev)) increasing intracellular Ca(2+) ([Ca(2+)](i)) which in turn will induce hypertrophy. The objective of this work was to test whether the inhibition of NHE-1 or NCX(rev) prevents ET-1 induced hypertrophy in neonatal rat cardiomyocytes (NRVMs). NRVMs were cultured (24 h) in the absence (control) and presence of 5 nmol/L ET-1 alone, or combined with 1 mumol/L HOE 642 or 5 mumol/L KB-R7943. Cell surface area, (3)H-phenylalanine incorporation and atrial natriuretic factor (ANF) mRNA expression were increased to 131 +/- 3, 220 +/- 12 and 190 +/- 25% of control, respectively (P < 0.05) by ET-1. [Na(+)](i) and total [Ca(2+)](i) were higher (8.1 +/- 1.2 mmol/L and 636 +/- 117 nmol/L, respectively) in ET-1-treated than in control NRVMs (4.2 +/- 1.3 and 346 +/- 85, respectively, P < 0.05), effects that were cancelled by NHE-1 inhibition with HOE 642. The rise in [Ca(2+)](i) induced by extracellular Na(+) removal (NCX(rev)) was higher in ET-1-treated than in control NRVMs and the effect was prevented by co-treatment with HOE 642 or KB-R7943 (NCX(rev) inhibitor). The ET-1-induced increase in cell area, ANF mRNA expression and (3)H-phenylalanine incorporation in ET-1-treated NRVM were decreased by NHE-1 or NCX(rev) inhibition. Our results provide the first evidence that NCX(rev) is, secondarily to NHE-1 activation, involved in ET-1-induced hypertrophy in NRVMs.
authors.affiliation: Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, UNLP, 60 y 120, 1900, La Plata, Argentina.
authors.forename: Raúl A
authors.initials: RA
authors.lastname: Dulce
authors.forename: Cecilia
authors.initials: C
authors.lastname: Hurtado
authors.forename: Irene L
authors.initials: IL
authors.lastname: Ennis
authors.forename: Carolina D
authors.initials: CD
authors.lastname: Garciarena
authors.forename: María C
authors.initials: MC
authors.lastname: Alvarez
authors.forename: Claudia
authors.initials: C
authors.lastname: Caldiz
authors.forename: Grant N
authors.initials: GN
authors.lastname: Pierce
authors.forename: Enrique L
authors.initials: EL
authors.lastname: Portiansky
authors.forename: Gladys E
authors.initials: GE
authors.lastname: Chiappe de Cingolani
authors.forename: María C
authors.initials: MC
authors.lastname: Camilión de Hurtado
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D009320:Atrial Natriuretic Factor / Q000378:metabolism; D006332:Cardiomegaly / Q000378:metabolism*; D019332:Endothelin-1 / Q000494:pharmacology*; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D019831:Sodium-Calcium Exchanger / Q000378:metabolism*; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*
chemical_list: D019332:Endothelin-1; D012333:RNA, Messenger; D019831:Sodium-Calcium Exchanger; D017923:Sodium-Hydrogen Exchangers; C069139:growth factor-activatable Na-H exchanger NHE-1; D009320:Atrial Natriuretic Factor