E. Borda et al., CIRCULATING ANTIBODIES AGAINST NEONATAL CARDIAC MUSCARINIC ACETYLCHOLINE-RECEPTOR IN PATIENTS WITH SJOGRENS-SYNDROME, Molecular and cellular biochemistry, 164, 1996, pp. 335-341
Isolated congenital heart block may be associated with Primary Sjogren
's Syndrome. In this work we demonstrated that IgG present in the sera
of patients with Primary Sjogren's Syndrome (PSS) could bind and acti
vate muscarinic acetylcholine receptors of rat neonatal atria. These a
ntibodies were able to inhibit in a irreversible manner the binding of
H-3-QNB to muscarinic cholinergic receptors of purified rat atria mem
branes. Moreover, IgG from PSS individuals could modify biological eff
ects mediated by muscarinic cholinoceptors activation, i.e. decrease c
ontractility and cAMP and increase phosphoinositide turnover and cGMP.
Atropine blocked all of these effects and carbachol mimicked them; co
nfirming muscarinic cholinergic receptors-mediated PSS IgG action. Nei
ther binding nor biological effect were obtained using adult instead o
f neonatal rat atria. Ige from sera of normal women were not effective
in the studied system. The prevalence of cholinergic antibody was 100
% in PSS and was independent of Ro/SS-A and La/SS-B antibodies. It cou
ld be concluded that antibody against muscarinic cholinergic receptors
may be another serum factor to be considered in the pathophysiology o
f the development of congenital heart block.