Gáspár R, Panyi G, Ypey D L, Krasznai Z, Vereb G, Pieri C, Damjanovich S
Department of Biophysics, University Medical School, Debrecen, Hungary.
Mol Pharmacol. 1994 Oct;46(4):762-6.
Using the patch-clamp technique, we determined that bretylium tosylate, a quaternary ammonium compound possessing immunomodulating activity, decreased the whole-cell K+ current in human T lymphocytes, in a dose-dependent manner, in the 0.05-5 mM extracellular concentration range. Bretylium tosylate prolonged the recovery from inactivation and accelerated the inactivation and deactivation of the K+ current but did not influence the kinetics of activation or the voltage dependence of activation and steady state inactivation of the K+ conductance. The percentage of drug-induced block was independent of membrane potential. K+ channel block by bretylium tosylate was partially and slowly removable by washing with drug-free extracellular solution. Bovine serum albumin (10 mg/ml) in the bath lifted the drug-induced block almost instantaneously, although not completely. In control experiments bovine serum albumin increased the inactivation time constant of the K+ channels but left the peak K+ current amplitude unaffected. On the basis of the experimental evidence, a gating-dependent allosteric interaction is suggested for the mechanism of drug action. The effective dose range, time of exposure, and reversibility of bretylium tosylate-induced K+ channel block correlated well with the same parameters of the drug-induced inhibition of T lymphocyte activation. The reported effects of bretylium tosylate on T cell mitogenesis can be regarded partly as a consequence of its blocking effects on voltage-gated K+ channels.
运用膜片钳技术，我们确定了托西溴苄铵（一种具有免疫调节活性的季铵化合物）在细胞外浓度为0.05 - 5 mM范围内，以剂量依赖的方式降低人T淋巴细胞的全细胞钾电流。托西溴苄铵延长了失活后的恢复时间，加速了钾电流的失活和去激活，但不影响激活动力学或钾电导激活和稳态失活的电压依赖性。药物诱导的阻断百分比与膜电位无关。用无药物的细胞外溶液冲洗可部分且缓慢地消除托西溴苄铵对钾通道的阻断作用。浴槽中的牛血清白蛋白（10 mg/ml）几乎能瞬间解除药物诱导的阻断，尽管不完全。在对照实验中，牛血清白蛋白增加了钾通道的失活时间常数，但不影响钾电流峰值幅度。基于实验证据，提示药物作用机制为门控依赖性变构相互作用。托西溴苄铵诱导的钾通道阻断的有效剂量范围、暴露时间和可逆性与该药物诱导的T淋巴细胞激活抑制的相同参数密切相关。托西溴苄铵对T细胞有丝分裂的报道效应可部分归因于其对电压门控钾通道的阻断作用。
