BETA-ADRENOCEPTOR SUBTYPES IN THE ATRIOVENTRICULAR CONDUCTING SYSTEM AND MYOCARDIUM OF SPONTANEOUSLY HYPERTENSIVE RATS - EFFECTS OF ANGIOTENSIN-CONVERTING ENZYME-INHIBITION BY PERINDOPRIL

Quantitative autoradiography was used to determine the density and dis tribution of beta(1)- and beta(2)-adrenoceptors in the atrioventricula r (AV) conducting system and surrounding myocardium of spontaneously h ypertensive rats (SHR) after chronic infusion of perindopril (1 mg/kg/ day) for 14 days by osmotic mini-pumps. Systolic blood pressure (SBP) was measured for a period of 4 weeks (2 weeks before and 2 weeks durin g perindopril infusion) in control and treated animals. Animals infuse d with vehicle (water) had a mean SBP of 248 mm Hg (measured on day 29 ); animals-treated with perindopril had lower SBP (121 mm Hg, day 29). Perindopril treatment also prevented development of cardiac hypertrop hy in SHR. beta-Adrenoceptor densities were measured in the AV node, H is bundle, left and right bundle branches (LB, BB), interventricular a nd interatrial septa (IVS, IAS), mitral valve (MV), right papillary mu scle, left and right ventricles (LV, RV), left and right atria (LA, RA ), and apex. Perindopril produced no significant change in beta-adreno ceptors in any cardiac region examined. The results suggest that under experimental conditions in which perindopril treatment prevented card iac hypertrophy and decreased SBP, there was no significant interactio n between the renin-angiotensin system (RAS) and beta-adrenoceptor sys tem in rat heart.