Escudero B, Gutiérrez-Merino C
Biochim Biophys Acta. 1987 Sep 3;902(3):374-84. doi: 10.1016/0005-2736(87)90205-7.
Sarcoplasmic reticulum vesicles are used here as model membrane system to question the hypothesis of enhancement of permeability of cations by anesthetics, particularly that of Ca2+ and of Mg2+. The effects of dibucaine (up to 800 microM), tetracaine (up to 2 mM), lidocaine (up to 10 mM) and procaine (up to 10 mM) on the permeability of these membranes to Ca2+ and Mg2+ have been measured. We have used an experimental approach based on the light scattering method (Kometani, T. and Kasai, M. (1978) J. Membrane Biol. 41, 295-308). It has been found that all the local anesthetics cited above markedly increase the permeability of sarcoplasmic reticulum vesicles to Mg2+ and, in the concentration range tested herein, only dibucaine and tetracaine increase the permeability to Ca2+. The kinetic analysis of the time dependence of the light-scattering data after the osmotic shock shows that, in the absence of local anesthetics, the Mg2+ influx can be described as proceeding through a unique type of channel. However, Ca2+ influx appears to involve two channel of different kinetic properties. Because the relative fraction of both types of Ca2+ channel is similar to the average ratio between light and heavy vesicles in unfractionated sarcoplasmic reticulum, we suggest that each type of channel can be preferentially located in one of these fractions. The determined rate constants for Ca2+ permeability through both types of channel are 0.77 +/- 0.08 min-1 (fast channels) and 0.025 +/- 0.005 min-1 (slow channels) and that for Mg2+ is 0.08 +/- 0.02 min-1. These results agree with data obtained by other groups using different experimental approaches. Dibucaine and tetracaine significantly alter the rate of Mg2+ and Ca2+ influx through the slow channels. In addition, these two local anesthetics also produce the effect that the Mg2+ influx cannot be described with only one exponential process, thus suggesting a differential effect on vesicles of different density. The increase of Ca2+ and Mg2+ permeability by dibucaine and by tetracaine is found at concentrations of these drugs that do not produce a noticeable inhibition of the (Ca2+ + Mg2+)-ATPase activity of sarcoplasmic reticulum vesicles.
在此，肌浆网囊泡被用作模型膜系统，以验证麻醉剂增强阳离子通透性这一假说，尤其是对Ca2+和Mg2+通透性的增强作用。已测定了丁卡因（浓度高达800微摩尔/升）、丁哌卡因（浓度高达2毫摩尔/升）、利多卡因（浓度高达10毫摩尔/升）和普鲁卡因（浓度高达10毫摩尔/升）对这些膜对Ca2+和Mg2+通透性的影响。我们采用了基于光散射法的实验方法（Kometani, T.和Kasai, M. (1978) J. Membrane Biol. 41, 295 - 308）。已发现上述所有局部麻醉剂均显著增加肌浆网囊泡对Mg2+的通透性，并且在本文测试的浓度范围内，只有丁卡因和丁哌卡因增加对Ca2+的通透性。对渗透休克后光散射数据的时间依赖性进行动力学分析表明，在无局部麻醉剂的情况下，Mg2+内流可描述为通过一种独特类型的通道进行。然而，Ca2+内流似乎涉及两种具有不同动力学特性的通道。由于两种类型的Ca2+通道的相对比例类似于未分级肌浆网中轻、重囊泡之间的平均比例，我们认为每种类型的通道可优先定位于其中一种组分中。通过两种类型通道的Ca2+通透性的测定速率常数分别为0.77±0.08分钟-1（快速通道）和0.025±0.005分钟-1（慢速通道），Mg2+的为0.08±0.02分钟-1。这些结果与其他研究小组使用不同实验方法获得的数据一致。丁卡因和丁哌卡因显著改变通过慢速通道的Mg2+和Ca2+内流速率。此外，这两种局部麻醉剂还产生了Mg2+内流不能仅用一个指数过程来描述的效应，从而表明对不同密度囊泡有不同的作用。在这些药物浓度下发现丁卡因和丁哌卡因增加Ca2+和Mg2+的通透性，而这些浓度并未对肌浆网囊泡的（Ca2+ + Mg2+）-ATP酶活性产生明显抑制。
