Storage and metabolism of norepinephrine after experimental myocardial infarction.

MATHES, PETER, CHARLES COWAN, AND SIGMUNDUR GUDBJARNASON. Storage and metabolism of norepinephrine after experimental myocar dial infarction. Am. J. Physiol. 220(l) : 27-32. 1971.-Serial determinations of the norepinephrine (NE) content in all four chambers of the canine heart were carried out following experimental myocardial infarction. Myocardial NE retention and subcellular distribution were determined after injection of tracer doses of dl-norepinephrine-7-14C. Normal left ventricular muscle contained 0.96 lug NE/g tissue; following coronary artery occlusion, the infarcted tissue lost its norepinephrine content completely by the 4th day and the noninfarcted tissue showed a marked decline during the first 10 days, reaching a level as low as 0.35 hug in the basilar and 0.14 pug NE/g in the apical portion of the left ventricle. The decrease in myocardial norepinephrine content extended to the right ventricle and both atria as well. Norepinephrine levels rose again 2 weeks after infarction and reached normal values 6 weeks after coronary artery occlusion. Despite these changes in endogenous norepinephrine levels, the myocardial retention of labeled NE, as well as the subcellular distribution of endogenous and exogenous NE, remained unaltered. Upon restoration of myocardial function, the cardiac norepinephrine content returns to normal.