Alterations in Cardiac β -Adrenoceptors During the Development of Rat Experimental Autoimmune Myocarditis

S ummary. In this study, we investigated changes in cardiac /?-adrenoceptor densities (Bmax) and affinities (dissociation constant: Kd) by Scachard analysis using the radioligand binding assay method during the development of rat experimental autoimmune myocarditis (EAM). Rats at ll weeks of age were subcutaneously injected in both foodpads with 0.2ml of antigenadjuvant emulsion for the induction of EAM. A peak increase in Bmaxvalues of cardiac muscles of EAM was observed at day 18 (active phase), followed by a tendency to decrease until day 214 after immunization. However, there were no changes in Kd values at any stage of EAM. Thus, the present study indicates that /?-AR densities change according to the stages of EAM. Key words-rat experimental autoimmune myocarditis, cardiac muscle /?-adrenoceptor,3H-CGP12177, radioligand binding assay.