Hencek M, Zacharová D, Zachar J
Centre of Physiological Sciences, Slovak Academy of Sciences, Bratislava.
Biomed Biochim Acta. 1989;48(5-6):S345-9.
The vaseline gap voltage clamp technique was used to study slow and fast calcium currents in phasic and tonic muscle fibres of the frogs Rana temporaria (R.t.) and Xenopus laevis (X.l.). At physiological Ca2+ and Na+ concentrations three inward currents could be recorded in R.t. twitch muscle fibres: a fast Ca current, a slow Ca current, and a non-specific (INS) current carried by Na ions. The last current appeared as a sole component at a low threshold membrane potential (MP -55 mV) and was present until the slow Ca current appeared. In tonic R.t. muscle and twitch X. laevis fibres only the fast and the slow Ca currents could be recorded; however the inactivation of the slow Ca current was very prolonged in the presence of Na ions. A modulatory effect of Na ions on Ca2+ currents was observed. In phasic fibres the fast Ca currents inactivated either very slowly or rapidly.
采用凡士林间隙电压钳技术研究了林蛙（Rana temporaria，R.t.）和非洲爪蟾（Xenopus laevis，X.l.）的相性和紧张性肌纤维中的慢钙电流和快钙电流。在生理Ca2+和Na+浓度下，可在R.t. 快肌纤维中记录到三种内向电流：快钙电流、慢钙电流和由Na离子携带的非特异性（INS）电流。最后一种电流在低阈值膜电位（膜电位 -55 mV）时作为唯一成分出现，并且在慢钙电流出现之前一直存在。在R.t. 紧张性肌纤维和X. laevis快肌纤维中只能记录到快钙电流和慢钙电流；然而，在存在Na离子的情况下，慢钙电流的失活非常延长。观察到Na离子对Ca2+电流有调节作用。在相性纤维中，快钙电流的失活要么非常缓慢，要么很快。
