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 Ca
2+
-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/Ca
2+
-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.
Inhibition of nitric oxide synthase augments the positive inotropic effect of nitric oxide donors in the rat heart
