The left main descending artery (LMDA) of left coronary artery (LCA) in rats runs around the left side of conus arteriosus after arising from the aortic sinus and descends to the apex of heart with branching several branches into the wall of left ventricle (LV). The ligation site of LMDA for myocardial infarction (MI) is the 2~4 mm from LCA origin, between the pulmonary trunk and left auricle. The characteristics that rat heart has no interventricular groove on the surface and its coronary arteries run intramyocardially with branching several branches give the difficulty in surgery for MI which resulted in expected size.

Although it has been reported that hormones or chemicals, which increse in intracellular cAMP, produced Mg2+ release from the heart, it is not well characterized whether a specific Mg2+ exchanger is involved in cAMP-induced Mg2+ efflux in themammalian hearts In this work, we studied the relationship between the increase in intracellular cAMP and ion transport system on Mg2+ regulation in the perfused rat heart and isolated myocytes. The Mg2+ content in the perfusate and supernatant were measured by atomic absorption spectrophotometer. The addition of membrane permeable cAMP analogue to the perfused hearts and myocytes. cAMP-induced Mg2+ efflux was ingibited by H7, benzamil or imipramine in the perfused hearts and myocytes, but not by EIPA. We confirmed that a significant Mg2+ efflux was induced by an increase in intracellular cAMP in the hearts and myocytes. The cAMP-induced increase of Mg2+ efflux in the hearts may be involved in ion transport system(Na+-Ca2+ and Na+-Mg2+ exchanger)

An 11-year-old, castrated male dog presented with a 3-month history of cough and depression. Auscultation revealed systolic murmur and thoracic radiographs showing enlargement of both the atrium and left ventricle. Echocardiography showed thickened mitral valve and moderate-to-severe left atrial enlargement. Additionally, M-mode echocardiography showed symmetric left ventricular wall thickening and systolic anterior motion of the mitral valve, while Doppler imaging revealed high velocity turbulent flow through the left ventricular outflow tract. Based on echocardiography, this case was diagnosed with hypertrophic obstructive cardiomyopathy. After 5 months, the dog was clinically static in radiography and echocardiography.