Effects of 12 Ca2+ antagonists on multidrug resistance, MDR1-mediated transport and MDR1 mRNA expression.
The effects of 12 Ca(2+) antagonists on MDR1 were examined by two independent models: the inhibitory effect on MDR1-mediated transport of [(3)H]digoxin using MDR1-overexpressing LLC-GA5-COL150 cell monolayers and the reversal effect on cytotoxicity of vinblastine or paclitaxel using MDR1-overexpressing Hvr100-6 cells. The inhibitory effects on [(3)H]digoxin transport were assessed as the 50% inhibitory concentration during 4 h exposure, and the values were the lowest for nicardipine (4.54 microM), manidipine (4.65 microM) and benidipine (4.96 microM), followed by bepridil (10.6 microM), barnidipine (12.6 microM), efonidipine (13.0 microM), verapamil (13.2 microM) and nilvadipine (18.0 microM). The reversal effect on cytotoxicity was assessed by the 50% growth inhibitory concentration after 3 days exposure, and the resistance to vinblastine or paclitaxel in Hvr100-6 cells was reversed by manidipine, verapamil, benidipine, barnidipine, and nicardipine, in that order. Bepridil, barnidipine, efonidipine, verapamil and nilvadipine showed similar inhibitory effects on [(3)H]digoxin transport, but barnidipine and verapamil showed a stronger effect in reversal of cytotoxicity. Real-time quantitative RT-PCR assay indicated a decrease in MDR1 mRNA expression by barnidipine and verapamil. It is concluded that Ca(2+) antagonists cannot only be direct inhibitors of MDR1 but that some may at the same time act as inhibitors of expression of MDR1 via down-regulation of MDR1 mRNA.
Department of Hospital Pharmacy, Faculty of Pharmaceutical Sciences, Kyoto Pharmaceutical University, 5 Nakauchi-Cho, Misasagi, Yamashina-Ku, Kyoto, 607-8414, Japan.
Kohji
K
Takara
Toshiyuki
T
Sakaeda
Yusuke
Y
Tanigawara
Kohshi
K
Nishiguchi
Nobuko
N
Ohmoto
Masanori
M
Horinouchi
Fusao
F
Komada
Noriaki
N
Ohnishi
Teruyoshi
T
Yokoyama
Katsuhiko
K
Okumura
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D000818:Animals; D001692:Biological Transport / Q000187:drug effects / Q000235:genetics; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002460:Cell Line; D004077:Digoxin / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D018432:Drug Resistance, Multiple / Q000235:genetics*; D015870:Gene Expression / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D009543:Nifedipine / Q000031:analogs & derivatives* / Q000494:pharmacology; D017239:Paclitaxel / Q000633:toxicity; D012333:RNA, Messenger / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D013552:Swine; D014316:Tritium; D014407:Tumor Cells, Cultured; D014700:Verapamil / Q000494:pharmacology; D014747:Vinblastine / Q000633:toxicity
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D002121:Calcium Channel Blockers; D012333:RNA, Messenger; D014316:Tritium; C050699:mepirodipine; D014747:Vinblastine; D004077:Digoxin; D014700:Verapamil; D009543:Nifedipine; D017239:Paclitaxel