Long-term postinfarction melatonin administration alters the expression of DHPR, RyR2, SERCA2, and MT2 and elevates the ANP level in the rat left ventricle

: We investigated the effect of 2 wk continuous postinfarction subcutaneous melatonin supply on the expression of the rat left ventricular (LV) dihydropyridine receptor (DHPR), ryanodine receptor (RyR2), and sarco‐endoplasmic reticulum Ca2+‐ATPase2 (SERCA2), as they are fundamental proteins in cardiac contractility. The levels of plasma and LV atrial (ANP) and brain natriuretic peptide and melatonin were also measured, as was the expression of LV MT1 and MT2 receptors and pineal arylalkylamine N‐acetyltransferase. Myocardial infarction (MI) was induced by ligation of the left anterior descending coronary artery and vehicle or melatonin (4.5 mg/kg per day) was administered by subcutaneous osmotic pumps. Echocardiography, real‐time quantitative reverse transcription‐polymerase chain reaction, and western blotting were used to analyze the samples. Echocardiography revealed that MI induced serious systolic LV dysfunction. The expression of DHPR, RyR2, and SERCA2 mRNAs was significantly lower in the LVs of melatonin‐treated MI rats compared with vehicle‐treated rats (P