Detection of mRNA encoding H1 receptor and iNOS by RT-PCR in autoimmune myocarditis with special reference to changes in heart contractility

Cardiac tissue from autoimmune myocarditis mice was studied to evaluate the expression and biological activity of mRNA encoding H1 receptor and iNOS. BALB/c inbred mice were immunized with heart protein and sacrificed at 20, 45 and 50 days post immunization. Heart contractility studies and RT-PCR assays were performed. Heart from autoimmune myocarditis mice show mRNA iNOS-related dysfunction with a decrease in heart contractility. This effect was accompanied with an increase production of cyclic GMP and was improved by treating autoimmune mice with an inhibitor of iNOS activity. In addition, autoimmune myocardium expressed an active histamine H1 receptor mRNA coupled to phospholipase C. The activation of H1 receptor by ThEA stimulated both phosphoinositide hydrolysis and heart contractility. Normal myocardium did not expressed neither iNOS mRNA nor H1 receptor mRNA. In conclusions: the development of autoimmune cardiac dysfunction was associated with the expression of iNOS mRNA, cyclic GMP accumulation and the expression of an active histamine H1 receptor mRNA with increase production of inositol phosphates. These protein emergence during the course of autoimmune myocarditis may be involved a distinct compensatory mechanism operating in this disease.