Alterations in the regional β adrenergic system in experimental left ventricular hypertrophy

Study objective – The aim of the study was to determine the changes in the β adrenergic system induced by cardiac hypertrophy due to valvular aortic stenosis. Design – Density of β adrenoceptors, cardiac tissue noradrenalime concentrations, coronary blood flow (using radioactive microspheres), and haemodynamic variables were compared in a model of experimental aortic valve stenosis of 6 month's duration and in sham operated controls. Subjects – 14 mongrel dogs with aortic stenosis and eight sham operated litter mates were used in the studies. Measurements and results – Heart weight to body weight ratio was 33% greater in dogs with aortic valve stenosis than in controls. There were no haemodynamic differences except for a left ventricular to aortic systolic pressure gradient of 38 (SD 22) mm Hg in the aortic stenosis group. Response of left ventricular dP/dtmax to dopamine was similar in the two groups, as was coronary flow. Density of β adrenoceptors (Bmax) as measured by (125I)-iodopindolol binding was reduced in ventricles from the aortic stenosis group compared to control: 41.2(13.3) v 59.1(8.1) fmol·mg−1 protein, p