title: Mechanisms of increased myocardial contractility with hypertonic saline solutions in isolated blood-perfused rabbit hearts.
abstract: Hypertonic saline improves organ perfusion and animal survival during hemorrhagic shock because it expands plasma volume and increases tissue oxygenation. Because both decreased and increased myocardial performance have been reported with hypertonic saline, the effects of hyperosmolarity and the mechanism accounting for it were investigated in isolated blood-perfused rabbit hearts. Coronary blood flow (CBF), myocardial contractility, relaxation, and oxygen consumption were measured during administration of blood perfusates containing 140-180 mmol sodium concentrations ([Na+]). In two other series of experiments, the role of Na(+)-Ca2+ exchange in the inotropic effect of hyperosmolarity (160 mmol sodium concentration) and hypertonicity (sucrose) were also investigated. Hypertonic [Na+] induced a significant increase in contractility and relaxation, combined with a coronary vasodilation. Myocardial oxygen consumption (MVO2) increased at all hypertonic [Na+] without significant change in coronary venous oxygen tension (PVO2) and content (CVO2). Amiloride (0.3 mmol) inhibited the improved contractility observed with 160 mmol sodium. Similar Na(+)-Ca2+ exchanger blockade did not inhibit the inotropic effect of sucrose. These results confirm the positive inotropic effect of hypertonic [Na+]. The inhibition of this improvement by amiloride suggests that calcium influx through the sarcolemna could be the major mechanism of this effect.
authors.affiliation: Département d'Anesthésie Réanimation (Pr Viars), Hôpital Pitié-Salpétrière, Paris, France.
authors.forename: S
authors.initials: S
authors.lastname: Mouren
authors.forename: S
authors.initials: S
authors.lastname: Delayance
authors.forename: G
authors.initials: G
authors.lastname: Mion
authors.forename: R
authors.initials: R
authors.lastname: Souktani
authors.forename: J L
authors.initials: JL
authors.lastname: Fellahi
authors.forename: M
authors.initials: M
authors.lastname: Arthaud
authors.forename: J F
authors.initials: JF
authors.lastname: Baron
authors.forename: P
authors.initials: P
authors.lastname: Viars
mesh_terms: D000584:Amiloride / Q000494:pharmacology*; D000818:Animals; D003326:Coronary Circulation / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects*; D010101:Oxygen Consumption / Q000187:drug effects; D011817:Rabbits; D012462:Saline Solution, Hypertonic / Q000494:pharmacology*; D013268:Stimulation, Chemical; D014664:Vasodilation / Q000187:drug effects
chemical_list: D012462:Saline Solution, Hypertonic; D000584:Amiloride