Gene Activations of CYP2B1 and CYP3A1 by Dihydropyridine Calcium Channel Antagonists in the Rat Liver: the Structure-Activity Relationship

We investigated the gene activations of CYP2B1 and CYP3A1 by 1,4-dihydropyridine calcium channel antagonists, including nifedipine (Nif), nisoldipine (Nis), nitrendipine (Nit), nimodipine (Nim), and nicardipine (Nic), in the rat liver and their structure-activity relationships. All calcium channel antagonists used have nitrophenyl substituents at the 4-position of the dihydropyridine ring and their nitro group was located at o- or m-position. The m-nitro derivatives Nic, Nim, and Nit showed much higher capacities for activating CYP3A1 than the o-nitro derivatives Nif and Nis. On the other hand, in the activation of CYP2B1, the length of the side chain at the 3-position of the dihydropyridine ring was correlated with the activating capacity of each chemical, and Nif and Nit, with a shorter side chain than the other calcium channel antagonists examined, had potent capacities. The present findings suggest that the ability of dihydropyridine calcium channel antagonists to activate the CYP2B1 and CYP3A1 are mainly dependent on the length of the side chain at the 3-position of the dihydropyridine ring and the position of the nitro group in the nitrophenyl substituent, respectively.