CIRCULATING ANTIBODIES AGAINST NEUROTRANSMITTER RECEPTOR ACTIVITIES IN CHILDREN WITH CONGENITAL HEART-BLOCK AND THEIR MOTHERS

In this work we demonstrated that IgG present in the sera of patients with congenital heart block (CHB) and their mothers could bind and act ivate beta adrenoceptors and muscarinic cholinergic receptors of neona tal heart. These antibodies were able to inhibit in a noncompetitive m anner the binding of [H-3]QNB and [H-3]CGP to muscarinic cholinergic a nd beta adrenoceptors of purified neonatal rat myocardial membranes, r espectively. Moreover, IgG from children with CHB and their mothers co uld modify biological effects mediated by these neurotransmitter recep tors, i.e., heart contractility and cAMP production. Neither binding n or biological effects were obtained using adult instead of neonatal ra t atria. Both reactivities (adrenergic and cholinergic) were independe nt of Ro/SS-A and La/SS-B antibodies and were absent in the sera of no rmal women of childbearing age and of normal children. It could be con cluded that antibodies against cardiac neurotransmitter receptors may be another serum factor (or factors) to be considered in the pathophys iology of the development of CHB.