SPECIFIC BINDING OF 1-[2-(DIPHENYLMETHOXY)ETHYL]-4-(3-PHENYL PROPYL) PIPERAZINE (GBR-12935), AN INHIBITOR OF THE DOPAMINE TRANSPORTER, TO HUMAN CYP2D6

The binding of [H-3]1-[2-(diphenylmethoxy)ethyl]-4-(3-phenyl propyl) p iperazine (GBR-12935), an antagonist of the dopamine transporter, to h uman P450s expressed in yeast cells was investigated. Among the ten fo rms of human P450 tested (CYP1A1, 1A2, 2A6, 2B6, 2C8, 2C9, 2C18, 2D6, 2E1, and 3A4), [H-3]GBR-12935 bound most. strongly to CYP2D6. The calc ulated K-d of [H-3]GBR-12935 binding to CYP2D6 was 42.2 nM, indicating that GBR-12935 has a high affinity for CYP2D6. The characteristics of [H-3]GBR-12935 binding to CYP2D6 were investigated by competitive stu dies using several chemicals. The binding of [H-3]GBR-12935 to CYP2D6 was not changed by dopamine, suggesting that these binding sites are n ot dopamine-sensitive binding sites. The binding of [H-3]GBR-12935 to CYP2D6 was decreased partially by substrates or inhibitors of CYP2D is oforms (quinine, quinidine, propranolol, bufuralol, imipramine, and de sipramine). By means of binding studies using several forms of express ed human P450, we demonstrated that the CYP2D isoform is one GBR-12935 binding site that is insensitive to dopamine. (C) 1997 Elsevier Scien ce Inc.