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dc.contributor.authorFeuvray, Dfr_FR
dc.contributor.authorKarmazyn, Mfr_FR
dc.date.accessioned2012-08-23T13:56:19Z
dc.date.available2012-08-23T13:56:19Z
dc.date.issued1999fr_FR
dc.identifier.citationFeuvray, D - Karmazyn, M, Echangeur Na+/H+ et régulation du pH des myocytes cardiaques : de la physiologie à la physiopathologie., Med Sci (Paris), 1999, Vol. 15, N° 3; p.322-8fr_FR
dc.identifier.issn1958-5381fr_FR
dc.identifier.urihttp://hdl.handle.net/10608/1341
dc.description.abstractLe pH intracellulaire influence de multiples aspects de la fonction des cellules cardiaques, via ses effets sur l' activite d' enzymes du metabolisme, sur des conductances ioniques - membranaires, sur l' homeostasie du calcium intracellulaire et, plus directement, sur la sensibilite au calcium des elements contractiles. Il n' est donc pas surprenant que les cellules aient elabore divers mecanismes de transport membranaire pour regler leur pH interne. La regulation du pH intracellulaire est assuree essentiellement par l' activite de mecanismes membranaires capables de transporter des ions H+ et HCO3- a l' exterieur ou a l' interieur de la cellule. Ces mecanismes maintiennent ou tendent a ramener, s' il s' en ecarte, le pHi a sa valeur physiologique proche de 7,2. L' activite de ces proteines specialisees dans le transport d' acides, ou de bases, a travers la membrane, est finement controlee par le pH intracellulaire lui-meme, et reglee par des stimulus extracellulaires, voire des signaux intracellulaires. Les mecanismes membranaires alcalinisants sont particulierement sollicites dans une situation pathologique telle que l' ischemie du myocarde.fr
dc.description.abstractIntracellular pH (pHi) can exert profound effects on cardiac function and the cardiac myocyte possesses regulated mechanisms for maintaining intracellular pH at physiological values. Among these processes, the sodium-hydrogen exchanger (NHE) represents a major mode of proton extrusion after acidosis, although other regulatory processes such as bi carbonate-dependent transporters are also of importance. At the present time, six exchanger genes are known to exist in mammals. NHE1 has been recognized for some time as the ubiquitous "housekeeping" isoform. It is the sole isoform detectable in the cardiac myocyte and its function and regulation has the greatest relevance for cardiovascular physiology and pathology. The activity of NHE1 can be modulated by a number of growth factors, hormones and neurotransmitters. There is extensive evidence supporting the concept that the Na+/H+ exchange represents an effective target for pharmacologic intervention for the protection of the ischemic and reperfused myocardium. Earlier studies have relied to a large degree on the use of amiloride or amiloride analogues to assess the role of the exchanger in tissue injury. Their conclusions, which are based on the assumption that the amiloride effect is mediated by its specificity for NHE, are reinforced by the more recent studies in which a different class of highly potent (NHE1 inhibitors with dissimilar structure (such as the HOE 642) was used. Studies published within the pat few years have indeed supported the concept of NHE1 involvement in myocardial ischemic and reperfusion injury. Although the activity of the exchanger can be stimulated by ischemia, its stimulation is particularly strong at the time of reperfusion. The idiosyncrasies of nature, however, are often suggestive of much more complex consequences of homeostatic processes than are first apparent, and NHE activation is no exception. Accordingly, experimental evidence has shown that stimulation of the exchanger, despite its necessity for pH, restoration after acidosis, may contribute (likely together with another Na+-dependent process, the Na+-HCO3- symport) to myocardial injury. The concomitant influx of sodium ions creates an ionic imbalance that can also result in elevations in intracellular calcium concentrations through sodium-calcium exchange, thus producing potentially deleterious calcium overloading conditions. Therefore, the Na+/H+ exchange is a paradoxical phenomenon because it is a major mechanism for restoration of pHi after ischemia. As a consequence, however, cell injury occurs.en
dc.language.isofrfr_FR
dc.publisherMasson, Parisfr_FR
dc.rightsArticle en libre accèsfr
dc.rightsMédecine/Sciences - Inserm - SRMSfr
dc.sourceM/S. Médecine sciences [revue papier, ISSN : 0767-0974], 1999, Vol. 15, N° 3; p.322-8fr_FR
dc.titleEchangeur Na+/H+ et régulation du pH des myocytes cardiaques : de la physiologie à la physiopathologie.fr
dc.title.alternativeNa+/H+ exchange and pHi regulation in cardiac myocytes: Physiology and pathophysiology.fr_FR
dc.typeArticlefr_FR
dc.contributor.affiliationUniversite Paris XI, Laboratoire de physiologie cellulaire, Batiment 443, 91405 Orsay, France; Universite de Western Ontario, Department of pharmacology and toxicology, London, Ontario N6 5C1, Canada-
dc.identifier.doi10.4267/10608/1341


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