Fig. 1

Measurement strategy for autoantibodies directed against G-protein coupled receptors (GPCR-AAB) in the IgG of patients with prostate cancer using the bioassay of cultured spontaneously beating neonatal rat cardiomyocytes. The bioassay monitored the chronotropic activity of IgG resulting from the presence of positive and negative chronotropic GPCR-AABs. For GPCR-AAB differentiation and activity calculation, the bioassay was performed in two runs. The first run was performed in the absence of GPCR blockers and thereafter with successive addition of 0.1 µmol/l atropine and 0.1 µmol/l BQ123 to block the muscarinic receptor 2 and endothelin receptor A. The second run was performed in the absence of GPCR blockers and thereafter with successive addition of 0.1 µmol/l losartan, 0.1 µmol/l propranolol and 0.1 µmol/l prazosin to block the AT1, β-adrenergic, and α1-adrenergic receptors. Calculation of the GPCR-AAB activity: mixed GPCR-AAB activity = M2-AAB activity + ETA-AAB activity + β-AAB activity + AT1-AAB activity + α1-AAB activity. Blue arrows indicate the ETA-AAB activity. Green arrows indicate the α1-AAB activity