Smeland E, Bremnes R M, Fuskevag O M, Aarbakke J
Department of Pharmacology, University of Tromsø, Norway.
Anticancer Res. 1995 Jul-Aug;15(4):1221-5.
The effects of diltiazem (DIL), verapamil (VRP) and Ca2+ on the accumulation of methotrexate (MTX) were investigated in isolated rat hepatocytes. At the physiological 2 mM Ca2+, the calcium-channel blockers DIL (100 microM) and VRP (50 microM) significantly reduced the hepatocellular accumulation of MTX. By increasing the Ca2+ concentration to 7 mM control MTX levels (at 2 mM Ca2+) were restored with VRP, and resulted in MTX levels above the controls for DIL. Ca2+ at 7 mM significantly enhanced MTX accumulation in the hepatocyte suspensions after 60 min. The concentration time curves for MTX indicated that for the first 10 min influx was the dominating process. Dixon plot analysis of this uptake phase revealed Ki values of 140 microM for DIL and 75 microM for VRP. The data suggested that DIL was a non-competitive, and VRP a competitive inhibitor of MTX influx. Hence, the inhibitory effect on MTX accumulation mediated by DIL and VRP could be due to different mechanisms.
在分离的大鼠肝细胞中研究了地尔硫䓬（DIL）、维拉帕米（VRP）和钙离子（Ca2+）对甲氨蝶呤（MTX）蓄积的影响。在生理浓度2 mM Ca2+时，钙通道阻滞剂DIL（100 microM）和VRP（50 microM）显著降低了肝细胞对MTX的蓄积。将Ca2+浓度提高到7 mM时，VRP使MTX水平恢复到对照水平（2 mM Ca2+时），而DIL组MTX水平高于对照。7 mM Ca2+在60分钟后显著增强了肝细胞悬液中MTX的蓄积。MTX的浓度-时间曲线表明，在前10分钟内，内流是主要过程。对该摄取阶段进行狄克逊图分析显示，DIL的Ki值为140 microM，VRP的Ki值为75 microM。数据表明，DIL是非竞争性抑制剂，VRP是MTX内流的竞争性抑制剂。因此，DIL和VRP对MTX蓄积的抑制作用可能是由于不同的机制。
