Lizardi L, Garcia M C, Sanchez J A, Zuazaga C
Institute of Neurobiology, University of Puerto Rico Medical Sciences Campus, San Juan.
J Membr Biol. 1992 Aug;129(2):167-78. doi: 10.1007/BF00219512.
Voltage-clamp experiments using the three-microelectrode voltage clamp technique were performed on ventroabdominal flexor muscles of the crustacean Atya lanipes. Potassium and chloride currents were found to underlie the normal, passive response of the muscle. Blocking potassium currents with tetraethylammonium and replacing chloride ions with methanesulfonate did not unmask an inward current. By treating the muscle with the sulfhydryl-alkylating agent 4-cyclopentene-1,3-dione an inward current was detected. The current induced by the agent is carried by Ca2+, since it is abolished in Ca(2+)-free solutions. The induced Ca2+ current is detected at about -40 mV and reaches a mean maximum value of -78 microA/cm2 at ca. -10 mV. At this potential the time to peak is close to 15 msec. The induced Ca2+ current inactivated with 1-sec prepulses which did not elicit detectable Ca2+ current; the fitted hx curve had a midpoint of -38 mV and a steepness of 5.0 mV. Measurements of isometric tension were performed in small bundles of fibers, and the effects of the sulfhydryl-alkylating agents 4-cyclopentene-1,3-dione and N-ethylmaleimide were investigated. Tetanic tension was enhanced in a strictly Ca(2+)-dependent manner by 4-cyclopentene-1,3-dione. The amplitude of K+ contractures increased after treatment with N-ethylmaleimide. It is concluded that Ca2+ channels are made functional by the sulfhydryl-specific reagents and that the increase in tension is probably mediated by an increase in Ca2+ influx through the chemically induced Ca2+ channels.
使用三微电极电压钳技术对甲壳动物阿蒂亚拉尼佩什的腹侧腹部屈肌进行了电压钳实验。发现钾离子和氯离子电流是肌肉正常被动反应的基础。用四乙铵阻断钾离子电流并用甲磺酸盐替代氯离子并没有揭示出内向电流。用巯基烷基化剂4-环戊烯-1,3-二酮处理肌肉后检测到内向电流。该试剂诱导的电流由Ca2+携带，因为在无Ca(2+)的溶液中该电流消失。在约-40 mV时检测到诱导的Ca2+电流，在约-10 mV时达到平均最大值-78 μA/cm2。在此电位下，峰值时间接近15毫秒。用不引起可检测Ca2+电流的1秒预脉冲可使诱导的Ca2+电流失活；拟合的hx曲线中点为-38 mV，斜率为5.0 mV。在小纤维束中进行了等长张力测量，并研究了巯基烷基化剂4-环戊烯-1,3-二酮和N-乙基马来酰亚胺的作用。4-环戊烯-1,3-二酮以严格依赖Ca(2+)的方式增强强直张力。用N-乙基马来酰亚胺处理后，K+挛缩的幅度增加。得出的结论是，巯基特异性试剂使Ca2+通道具有功能，张力增加可能是由通过化学诱导的Ca2+通道的Ca2+内流增加介导的。
