Regulation of ß-adrenoceptors in the guinea-pig sinoatrial node

Abstract

This study examined the changes of ß-adrenoceptors in the guinea-pig sinoatrial nodal region following 7 day (-)-isoprenaline (400 μg/kg/h s.c.) infusion and the relationship between ß-adrenoceptor desensitization and receptor down-regulation. Changes in ß1-and ß2-adrenoceptor density were measured using quantitative autoradiography and function in organ bath studies. (-)-Isoprenaline treatment produced a marked decrease in total (from 57.5 to 33.9 fmol/mg protein), ß1-(from 49.4 to 32.8 fmol/mg protein), and ß2-adrenoceptor density (from 8.1 to 1.05 fmol/mg protein) in the sinoatrial node. In adjacent right atrium, treatment produced no change in total (39.5 and 36.7 fmol/mg protein) or ß1-..