AbstractsBiology & Animal Science

The effect of cold-storage was studied on rat atria. Storage did not change the spontaneous rate but caused a reduction in the contractility. Stored atria had a low intracellu1ar K+ concentration and had a reduced resting potential, action potential height, duration, area and depolarization rate. Incubation in low K+ produced an increase in the contractility of the stored but not of fresh atria. Fresh atria incubated in 12 mM K+ had electrophysiological characteristics similar to but had a contractile force greater than those of stored atria. ATP content of stored atria was reduced. Incubation of stored atria with adenosine increased the ATP content but not the contractility. The positive inotropic and chronotropic effects of noradrenaline, ouabain or Ca++ on fresh and stored atria were comparable. It was concluded that the decrease in contractility of stored atria was due partly to electrophysiological changes and partly to the reduced ATP content. The effect of cold-storage was studied on rat atria. Storage did not change the spontaneous rate but caused a reduction in the contractility. Stored atria had a low intracellu1ar K+ concentration and had a reduced resting potential, action potential height, duration, area and depolarization rate. Incubation in low K+ produced an increase in the contractility of the stored but not of fresh atria. Fresh atria incubated in 12 mM K+ had electrophysiological characteristics similar to but had a contractile force greater than those of stored atria. ATP content of stored atria was reduced. Incubation of stored atria with adenosine increased the ATP content but not the contractility. The positive inotropic and chronotropic effects of noradrenaline, ouabain or Ca++ on fresh and stored atria were comparable. It was concluded that the decrease in contractility of stored atria was due partly to electrophysiological changes and partly to the reduced ATP content.L'effet de la préservation par le froid a été étudié sur les oreillettes de rats. La préservation par le froid ne change pas la fréquence de contraction spontanée mais produit une diminution de la contractilité. Les oreillettes préservées ont une concentration basse en potassium intracellulaire, un potential de repos reduit ainsi qu'une diminution de l'amplitude, de la durée, de l'aire et de la rapidité de depolarisation du potentiel d'action. L'incubation du tissu dans un milieu pauvre en K+ produit une augmentation de la contractilité des oreillettes préservées au froid mais non des oreillettes fraîches. Les oreillettes fraîches, incubées dans un milieu contenant l2 mM K+, ont des caractéristiques électrophysiologiques semblables à celles des oreillettes préservées au froid, mais elles ont une force contractile superieure. L'incubation des oreillettes dans un milieu contenant de l'adénosine augmente leur contenu en ATP sans augmenter leur contractilité. Les effets inotrope et chronotrope de la noradrenaline, de la ouabain ou du Ca++ sont comparables sur les oreillettes franches et préservées. Il en est conclu que cette…