- RDC8 codes for an adenosine A2 receptor with physiological constitutive activity. Maenhaut, C., Van Sande, J., Libert, F., Abramowicz, M., Parmentier, M., Vanderhaegen, J.J., Dumont, J.E., Vassart, G., Schiffmann, S. Biochem. Biophys. Res. Commun. (1990)