Zahradník I, Zachar J
Centre of Physiological Sciences, Slovak Academy of Sciences. Bratislava, Czechoslovakia.
Gen Physiol Biophys. 1987 Apr;6(2):113-25.
Calcium currents in crayfish muscle fibres were studied by means of the vaseline gap voltage clamp technique. Overlapping potassium currents were fully suppressed using fibre fragments equilibrated in K+-free intracellular solution. The design of the recording chamber tailored to crayfish muscle fibres is described in detail. Ca currents recorded has a two-component time course. The transient (ICa, T) component (peaking in about 10 ms) attained, on average, maximal overall density of 26.4 microA/cm2 at depolarization to -4.6 mV from a holding potential of -80 mV. The steady (ICa, S) component attained 16.7 microA/cm2 (evaluated at the end of a 70 ms pulse) at +13.8 mV. The average overall surface area of the clamped membrane surface (including invaginated parts) was about 0.07 cm2. The ICa, S component could be separated from ICa, T using short inactivating prepulses. Voltage and time dependence of the transient component inactivation, as well as its recovery from inactivation, were in agreement with a Ca-dependent mechanism. Independent behaviour of the two Ca current components and differences in their properties support the hypothesis concerning the existence of two populations of Ca channels in the surface membrane of the crayfish muscle.
采用凡士林间隙电压钳技术研究了小龙虾肌肉纤维中的钙电流。使用在无钾细胞内溶液中平衡的纤维片段，完全抑制了重叠的钾电流。详细描述了针对小龙虾肌肉纤维设计的记录室。记录到的钙电流具有双成分时程。瞬态（ICa,T）成分（在约10 ms达到峰值），从-80 mV的钳制电位去极化到-4.6 mV时，平均最大总体密度达到26.4 μA/cm2。稳态（ICa,S）成分在+13.8 mV时达到16.7 μA/cm2（在70 ms脉冲结束时评估）。钳制膜表面（包括内陷部分）的平均总面积约为0.07 cm2。使用短的失活预脉冲可将ICa,S成分与ICa,T成分分离。瞬态成分失活的电压和时间依赖性及其从失活中的恢复，与钙依赖性机制一致。两种钙电流成分的独立行为及其特性差异支持了关于小龙虾肌肉表面膜中存在两种钙通道群体的假设。
