title: Hypotonic swelling promotes nitric oxide release in cardiac ventricular myocytes: impact on swelling-induced negative inotropic effect.
abstract: OBJECTIVE
  Cardiomyocyte swelling occurs in multiple pathological situations and has been associated with contractile dysfunction, cell death, and enhanced propensity to arrhythmias. We investigate whether hypotonic swelling promotes nitric oxide (NO) release in cardiomyocytes, and whether it impacts on swelling-induced contractile dysfunction.
  
  
  RESULTS
  Superfusing rat cardiomyocytes with a hypotonic solution (HS; 217 mOsm), increased cell volume, reduced myocyte contraction and Ca(2+) transient, and increased NO-sensitive 4-amino-5-methylamino-2',7'-difluorofluorescein diacetate (DAF-FM) fluorescence. When cells were exposed to HS + 2.5 mM of the NO synthase inhibitor l-NAME, cell swelling occurred in the absence of NO release. Swelling-induced NO release was also prevented by the nitric oxide synthase 1 (NOS1) inhibitor, nitroguanidine, and significantly reduced in NOS1 knockout mice. Additionally, colchicine (inhibitor of microtubule polymerization) prevented the increase in DAF-FM fluorescence induced by HS, indicating that microtubule integrity is necessary for swelling-induced NO release. The swelling-induced negative inotropic effect was exacerbated in the presence of either l-NAME, nitroguandine, the guanylate cyclase inhibitor, ODQ, or the PKG inhibitor, KT5823, suggesting that NOS1-derived NO provides contractile support via a cGMP/PKG-dependent mechanism. Indeed, ODQ reduced Ca(2+) wave velocity and both ODQ and KT5823 reduced the HS-induced increment in ryanodine receptor (RyR2, Ser2808) phosphorylation, suggesting that in this context, cGMP/PKG may contribute to preserve contractile function by enhancing sarcoplasmic reticulum Ca(2+) release.
  
  
  CONCLUSIONS
  Our findings suggest a novel mechanism for NO release in cardiomyocytes with putative pathophysiological relevance determined, at least in part, by its capability to reduce the extent of contractile dysfunction associated with hypotonic swelling.
authors.affiliation: Centro de Investigaciones Cardiovasculares, CONICET La Plata, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, 60 y 120, La Plata 1900, Argentina.
authors.forename: Luis Alberto
authors.initials: LA
authors.lastname: Gonano
authors.affiliation: Centro de Investigaciones Cardiovasculares, CONICET La Plata, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, 60 y 120, La Plata 1900, Argentina.
authors.forename: Malena
authors.initials: M
authors.lastname: Morell
authors.affiliation: Centro de Investigaciones Cardiovasculares, CONICET La Plata, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, 60 y 120, La Plata 1900, Argentina.
authors.forename: Juan Ignacio
authors.initials: JI
authors.lastname: Burgos
authors.affiliation: Interdisciplinary Stem Cell Institute, University of Miami Miller School of Medicine, Miami, FL, USA.
authors.forename: Raul Ariel
authors.initials: RA
authors.lastname: Dulce
authors.affiliation: Centro de Investigaciones Cardiovasculares, CONICET La Plata, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, 60 y 120, La Plata 1900, Argentina.
authors.forename: Verónica Celeste
authors.initials: VC
authors.lastname: De Giusti
authors.affiliation: Centro de Investigaciones Cardiovasculares, CONICET La Plata, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, 60 y 120, La Plata 1900, Argentina.
authors.forename: Ernesto Alejandro
authors.initials: EA
authors.lastname: Aiello
authors.affiliation: Interdisciplinary Stem Cell Institute, University of Miami Miller School of Medicine, Miami, FL, USA.
authors.forename: Joshua Michael
authors.initials: JM
authors.lastname: Hare
authors.affiliation: Centro de Investigaciones Cardiovasculares, CONICET La Plata, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, 60 y 120, La Plata 1900, Argentina mvila@med.unlp.edu.ar.
authors.forename: Martin
authors.initials: M
authors.lastname: Vila Petroff
mesh_terms: D000818:Animals; D006152:Cyclic GMP / Q000378:metabolism; D003599:Cytoskeleton / Q000502:physiology*; D008297:Male; D008810:Mice, Inbred C57BL; D009200:Myocardial Contraction; D032383:Myocytes, Cardiac / Q000502:physiology*; D009569:Nitric Oxide / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I / Q000378:metabolism; D064587:Osmoregulation; D017208:Rats, Wistar
chemical_list: D009569:Nitric Oxide; D052248:Nitric Oxide Synthase Type I; C496322:Nos1 protein, rat; D006152:Cyclic GMP
keywords: Contractile dysfunction; Hypotonic swelling; Ischaemia reperfusion; Nitric oxide