镉对心肌细胞Ca^2＋通道的阻滞作用及硒的保护效应

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。

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

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.