title: [Effect of the ventricular preload on the basal and stimulated coronary circulation of the isolated rat heart].
abstract: Langendorff perfused isolated rat heart is a common model for coronary blood flow study. Left ventricular preload can both increase coronary blood flow by direct inotropic effect or decrease it by rising transmural tension. Experiments were designed to determine optimal preload conditions for observation of basal (CBF) and 5-hydroxytryptamine (5-HT) stimulated coronary blood flow (SCBF) in the isolated rat heart model. Rat hearts (n = 6) were harvested and stabilized in the Langendorff apparatus and a left ventricular balloon was inserted and inflated at different volumes (0.05 to 0.4 ml) to stimulate preload. Left ventricular systolic (LVSP), diastolic (LVDP), myocardial oxygen consumption (MVO2) and extraction (MEO2) were also measured. Under basal conditions, optimal LVSP was obtained at 0.2 ml (111 +/- 15 mmHg). MVO2 was optimal at 0.2 ml of preload and decreased thereafter while MEO2 remained stable. Optimal CBF was reached at 0.2 ml of preload. Under 5-HT stimulation, CBF increased significantly (CBF: 8.2 +/- 0.6 ml/min vs SCBF: 16.4 +/- 1.0 ml/min, p < 0.01) while left ventricular hemodynamics did not differ from basal observations. At preload volume > 0.2 ml a significant drop in SCBF was observed (0 ml: 16.4 +/- 1 ml/min vs 0.4 ml: 11 +/- 1 ml/min, p < 0.01). MVO2 and MEO2 followed the same pattern observed under basal conditions. In basal and stimulated conditions, a hyperemic flow was also seen after deflation of the balloon with preload > = 0.2 ml in both CBF and SCBF suggesting myocardial oxygen debt. We conclude that in the Langendorff model preload affects coronary flow under both basal and 5-HT stimulation. A volume > 0.2 ml for rats of 350-400 g can impede CBF and generate myocardial oxygen debt as suggested by a decreased MVO2 and a post-deflation hyperemic flow. Left ventricular preload should be maintained under 0.2 ml for optimal coronary blood flow study in the Langendorff perfused rat heart model.
authors.affiliation: Service de Chirurgie, Institut de Cardiologie de Montréal, Québec, Canada.
authors.forename: J F
authors.initials: JF
authors.lastname: Latulippe
authors.forename: J
authors.initials: J
authors.lastname: Buluran
authors.forename: R
authors.initials: R
authors.lastname: Cartier
mesh_terms: D000818:Animals; D003326:Coronary Circulation / Q000187:drug effects*; D006321:Heart / Q000502:physiology; D006439:Hemodynamics; D066298:In Vitro Techniques; D008954:Models, Biological; D009200:Myocardial Contraction; D010101:Oxygen Consumption; D051381:Rats; D017207:Rats, Sprague-Dawley; D012701:Serotonin / Q000494:pharmacology; D014655:Vascular Resistance / Q000187:drug effects; D016277:Ventricular Function, Left
chemical_list: D012701:Serotonin