TRIFUNCTIONAL LIGANDS: A RADIOIODINATED HIGH AFFINITY ACYLATING ANTAGONIST FOR THE A1ADENOSINE RECEPTOR.
A new xanthine (adenosine antagonist) radioligand that binds covalently to A1-adenosine receptors was prepared and used as a receptor probe. BH-DITC-XAC was synthesized via a trifunctional aryl diisothiocyanate crosslinker. containing the p-hydroxyphenylpropionyl group for radioiodination. The xanthine competed against agonist or antagonist A1receptor radioligands in bovine brain membranes with an IC50, of 40nM.125I-BH-DITC-XAC, prepared directly by the chloramine T method and purified by HPLC. bound specifically to A1receptors. This binding was inhibited in the presence of the adenosine agonistsR-PIA,S-PIA. and NECA in a dose dependent manner and with the order of potency characteristic of bovine A1receptors. Incubation of affinity purified bovine A1-receptors with125I-BH-DITC-XAC (0.8 nM) for 2 hours resulted in the specific and clean labelling of a polypeptide band corresponding to MW 36,000, identical to that previously found for the A1receptor.
Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892.
Kenneth A
KA
Jacobson
Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892.
Mark E
ME
Olah
Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892.
Gary L
GL
Stiles
adenosine receptors; affinity labeling; radioiodination; xanthines