Alterations in the regional beta adrenergic system in experimental left ventricular hypertrophy.
STUDY OBJECTIVE - The aim of the study was to determine the changes in the beta adrenergic system induced by cardiac hypertrophy due to valvular aortic stenosis. DESIGN - Density of beta 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 beta 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 less than 0.005. Affinity of receptor for ligand (Kd) was not affected by cardiac hypertrophy. Tissue noradrenaline concentration was reduced in the hypertrophy group: 1108(402) (control) v 438(13) ng.g-1 initial wet weight (aortic stenosis), p less than 0.05. There were no significant subepicardial v subendocardial differences in any variable. CONCLUSIONS - Cardiac hypertrophy induced by aortic valve stenosis over a 6 month period is accompanied by a decrease in the density of ventricular beta adrenoceptors per gram and a decrease in ventricular noradrenaline concentration, though responsiveness of the whole heart is maintained.
Scholz
P M
PM
Department of Surgery, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Piscataway 08854-5635.
Upsher
M E
ME
Eliades
D
D
Kedem
J
J
Weiss
H R
HR
D000818:Animals; D001024:Aortic Valve Stenosis / Q000150:complications / Q000378:metabolism; D006332:Cardiomegaly / Q000209:etiology / Q000378:metabolism / Q000503:physiopathology*; D004195:Disease Models, Animal; D004285:Dogs; D006321:Heart / Q000033:anatomy & histology; D006352:Heart Ventricles / Q000032:analysis; D009638:Norepinephrine / Q000032:analysis; D009929:Organ Size / Q000502:physiology; D011943:Receptors, Adrenergic, beta / Q000032:analysis; D013564:Sympathetic Nervous System / Q000503:physiopathology*
D011943:Receptors, Adrenergic, beta; D009638:Norepinephrine