Abstract 2192: Fcgamma Receptor II On Cardiomyocytes
Introduction: Recently we detected the FcγII receptor on rat and human cardiomyocytes. Binding of cardiac antibodies obtained from DCM-patients to this receptor induced negative inotropic effects. The mechanism of these effects remains to be elucidated.
Methods: Isolated adult rat cardiomyocytes stained with Fura-2-AM were field-stimulated (1 Hz, 12 V). The relative change of the calcium transients and systolic cell shortening due to superfusion with a polyclonal goat-antibody against the FcγII receptor (10 μg/ml) were recorded with a dual-excitation fluorescence microscope. For inhibition of possible involved tyrosine kinases we used PP2 (1μM) and specific syk-Kinase inhibitors.
Results: Superfusion of rat cardiomyocytes with anti-FcγII-receptor antibody induces a negative inotropic effect. The tested concentrations (6 μg/ml, 8 μg/ml, 10 μg/ml and 16 μg/ml) show a clear dose-response-relationship. The contractility of the cells decreases after 2 min by −5,3%, −11,5%, −14,2% and −18,3% from baseline as well as the Ca2+-Ratio (−9,5%, −11,2%, −12,2%, −15,6%). The negative inotropic reaction could be blocked by preincubation of the cells with the tyrosine kinase inhibitor PP2 (change of contractility/Ca2+-Ratio from baseline: −1, 3%/−2,4%, p<0,001). Cells preincu-bated with specific inhibitors for syk-Kinases did not show a negative inotropic reaction after superfusion with the antibody (change of contractility/Ca2+-ratio from baseline +0,7%/−5,5%, p<0,05). A polyclonal goat control antibody (anti-CD45, c = 10 μg/ml)) did not trigger a reaction (change from baseline for contractility/Ca2+-Ratio: −3%/−2,4%, p<0,001).
Conclusion: The inhibition of the negative inotropic effect of antibodies against FcγII receptor shows an involvement of Kinases in the signalling pathway like described for other cell types.