Vicious Cycle of Catecholamines and K+ in Cardiac Ischemia

The distribution of catecholamine (CA)-containing neurones and tissue noradrenaline (NA) concentration was investigated in pig hearts with and without myocardial ischemia. All hearts were shock-frozen using a Wollenberger clamp, and tissue samples were obtained from the mid- and apical left ventricular wall (nonischemic and ischemic areas, respectively, in hearts with coronary artery occlusion). The distribution of CA-containing neurones was assessed morphometrically from histofluorescence sections, and the NA content measured using high pressure liquid chromatography (HPLC). In hearts without myocardial ischemia, both the density of CA-containing neurones (0.96 +/- 0.07 compared with 1.09 +/- 0.07% of total field area) and the NA content (738 +/- 63 compared with 884 +/- 84 ng/g wet weight, p less than 0.025) were less in apical samples compared with those obtained at the midventricular level. These differences were more pronounced in samples from hearts obtained following 5 min (fluorescence, 0.96 +/- 0.19 compared with 1.38 +/- 0.18%, p less than 0.01; NA content, 543 +/- 109 compared with 816 +/- 82 ng/g wet weight, p less than 0.01) or 15 min (fluorescence, 0.77 +/- 0.07 compared with 1.12 +/- 0.09%; NA content, 521 +/- 43 compared with 753 +/- 79 ng/g wet weight, p less than 0.01) of coronary artery occlusion, indicating a release of CA in the ischemic myocardium.