A CIRCULATING IGG IN CHAGAS-DISEASE WHICH BINDS TO BETA-ADRENOCEPTORS OF MYOCARDIUM AND MODULATES THEIR ACTIVITY

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  • 1 January 1984
    • journal article
    • research article
    • Vol. 57  (3) , 679-686
Abstract
Sera from chagasic patients with positive EVI (laminin) serology can act in cooperation with complement or normal human lymhocytes as a partial .beta.-adrenoceptor agonist increasing the contractile tension and frequency of isolated rat atria, as occurs with IgG purified from chagasic serum. This paper demonstrates that IgG present in chagasic patients sera could bind to the .beta.-adrenoceptors of the heart and stimulate contractile activity of myocardium. The positive inotropic and chronotropic effect could be blocked by the specific .beta.1-adrenoceptor antagonist but not by the .beta.2-adrenoceptor antagonist. Chagasic IgG inhibited the binding of (-) 3H-DHA to .beta.-adrenoceptors of purified rat myocardial membranes behaving as noncompetitive inhibitors. The reactivity of chagasic serum or IgG with .beta.1-adrenoceptor was lost after absorptions with turkey red blood cells. Guinea pig red blood cells were unable to remove the .beta.1 reactivity of chagasic serum or chagasic IgG. This supports the specificity of .beta.1-adrenoceptors of the chagasic IgG and the independence of .beta.1-adrenoceptor reactivity in relation to the EVI system. Clinical specificity of the .beta.1-adrenoceptor reactivity seems rather high in Chagas'' disease since it was lacking in 14 individuals with other cardiopathies, such as ischemic and rheumatic heart disease, even after heart surgery.