Eect of Melatonin on the Isolated Heart in the Standard Perfusion Conditions and in the Conditions of Calcium Paradox

Abstract. The eect of melatonin (MLT) on the isolated rat heart was studied using the standard perfusion conditions (Langendor preparation) and model of calcium paradox (Ca2+-paradox). Ca2+-paradox was induced by 1 minute perfusion with Ca2+-free Krebs-Henseleit (KH) solution and subsequent 20 minutes perfusion with a normal Ca2+-containing KH solution. In MLT group, MLT (10 mol/l) was in the perfusion solution throughout the experiment. In controls, there was no MLT. Variables: heart rate, coronary flow, systolic and diastolic pressure, +dP=dt max (index of contractility) and −dP=dt max (index of relaxation) were measured at the end of stabilization, i.e. after 30 minutes of standard perfusion and then in the 5th, 10th, 15th, 20th minute after perfusion with Ca2+-free KH solution. Results: There was no dierence between MLT group and controls in the standard perfusion conditions at the end of stabilization. After perfusion with Ca2+-free KH solution, systolic-diastolic dierence (in the 10th, 15th, 20th minute), +dP=dt max (in the 5th, 10th, 15th, 20th minute) and −dP=dt max (in the 15th minute) were signi cantly decreased in MLT group in comparison to controls. Conclusion: Melatonin didn’t influence rat isolated heart in standard perfusion conditions but it made the heart more susceptible to Ca2+-paradox