镉对心肌细胞Ca^(2+)通道的阻滞作用及硒的保护效应

Blocking action of cadmium on calcium channels of the cultured cardiac cells and protective effects of selenium

目的探讨镉（Ｃｄ）对心肌细胞Ｃａ２＋通道阻滞作用的机制，比较亚硒酸钠（ＮａＳｅ）与硒代蛋氨酸（ＳｅＭｅｔ）两种硒化合物的保护效应。方法在培养的Ｗｉｓｔａｒ大鼠心肌细胞上观察Ｂ、Ｌ、Ｔ三型Ｃａ２＋通道的单通道电活动。结果Ｃｄ浓度为１０μｍｏｌ／Ｌ时，心肌细胞Ｂ、Ｌ型Ｃａ２＋通道受到明显阻滞；而对Ｔ型Ｃａ２＋通道没有影响。在加入Ｃｄ的同时，分别加入等浓度的ＮａＳｅ和ＳｅＭｅｔ，ＮａＳｅ能拮抗Ｃｄ对Ｂ、Ｌ型Ｃａ２＋通道的阻滞作用，ＳｅＭｅｔ仅能减轻Ｃｄ对Ｌ型Ｃａ２＋通道的阻滞，而且使Ｔ型Ｃａ２＋通道的关闭时间延长。结论Ｃｄ对心肌细胞Ｂ、Ｌ型Ｃａ２＋通道具有明显的阻滞作用，而对Ｔ型Ｃａ２＋通道没有影响；两种硒化合物均可影响Ｃｄ致心肌细胞膜Ｃａ２＋通道的阻滞作用，ＮａＳｅ的保护作用比ＳｅＭｅｔ更有效。

Objective To study the effects of cadmium on the single channel activities of Btype,Ltype and Ttype Ca2+ channels of cultured ventricular myocytes of neonatal Wistar rats and the protective effects of selenium. Methods Patch clamp technique was conducted in the study.The opening of L and T type calcium channels were evoked by a depolarizing test pulse from -50 to +10 mV and from -70 to -10 mV respectively,while B type calcium channel was recorded at -60 mV without depolarizing test pulse. Results Cadmium at dose of 10 mol/L significantly inhibited the activities of Btype and Ltype Ca2+ channels but not on Ttype Ca2+ channel.The open time of Btype and Ltype Ca2+ channels shortened by 33.5% and 40.7% respectively and the openstate probability(Po) of them decreased by 55.0% and 50.0% respectively,whereas there was no significant variation in the amplitude of ionic current flowing(Iba) through the Ca2+ channels.When selenium and cadmium were added in equal molarity(10 mol/L) simultaneously,sodium selenite could antagonize the inhibition of Cd on B and L type Ca2+ channels,while selenomethionine only attenuated the inhibition on L type Ca2+ channel. Conclusion Both sodium selenite and selenomethionine had protective effects on cadmiuminduced inhibition of Ca2+ channels,and sodium selenite was more effective than selenomethionine.