Refined membrane preparations mask ischemic fall in myocardial beta -receptor density

Most of the previous studies of ischemic myocardial beta -adrenergic receptors have employed membrane preparations in which the initial pellet from the myocardial homogenate spun at a low speed was discarded. We studied changes in beta -adrenergic receptor density (( super(125)I)-iodocyanopindolol; B sub(max)) during 30 min of coronary occlusion in surgically anesthetized open-chest rabbits using just such a pellet (homogenized heart spun at 1,000 g (1,000-g pellet)), as well as a second pellet from the supernatant of the first pellet (spun at 40,000 g (40,000-g pellet)).