CHANGES IN HOLDING AND ION-CHANNEL CURRENTS DURING ACTIVATION OF AN ASCIDIAN EGG UNDER VOLTAGE CLAMP
CHANGES IN HOLDING AND ION-CHANNEL CURRENTS DURING ACTIVATION OF AN ASCIDIAN EGG UNDER VOLTAGE CLAMP
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DOI：
10.1113/jphysiol.1982.sp014072
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发表时间：
1982-01-01
影响因子：
5.5
通讯作者：
TAKAHASHI, K
中科院分区：
文献类型：
--
作者：
KOZUKA, M;TAKAHASHI, K
海鞘H. roretzi，被激活的二价离子载体A23187 [calcimycin]在天然[nSW]或人工海水（ASW）或由外部溶液含有高浓度的Ca 2+（高钙ASW）在电压钳条件下。激活电流开始与突然增加的保持电流和衰减相对缓慢的一个共同的时间过程中，在各种ASW。激活电流同时具有钠和钙依赖性。在15 ° C下，以nSW为单位的激活电流的峰值时间Tp和峰值幅度D。C和-90 mV的平均电压为27 ± 0.5mV。4s和-1.50 .+-. 0.47 nA，分别。在nSW和高Sr、高Ca和高K ASW中，用恒定间隔的测试脉冲诱发Na、Ca和异常K通道电流。Na通道电流在激活过程中增强。钙通道电流降低。在高钙无钠的ASW中，通过Na通道的Ca电流增加，而通过Ca通道的Ca电流减少。Na电流最大值的时间Tmax为（7.2 ± 0.01）min。1.5). times. 15度时10秒。C和指数R，即最大振幅与激活前振幅的比值，为2.31 ± 0.01。0.18在NSW。Ca-通道电流最小的时间Tmin为70 s，与Na电流的Tmax几乎相同。通过异常钾通道的电流先增加后减少，滞后于钙通道电流的减少。随着温度的升高，激活电流的Tp和钠电流的Tmax均降低。Tp和Tmax的Q10分别为2.2和2.3。当卵被蝎毒素激活时，正常通道的Na+电流显著增加，而毒素修饰通道的Na+电流增加不明显。在活化前和活化过程中，总膜容量没有显著变化。
The unfertilized egg of an ascidian, H. roretzi, was activated by the divalent ionophore A23187 [calcimycin] in natural-[nSW] or artificial sea water (ASW) or by an external solution containing a high concentration of Ca2+ (high-Ca ASW) under voltage-clamp condition. Activation current began with an abrupt increase in the holding current and decayed relatively slowly with a common time course in various ASW. Activation current was both Na- and Ca-dependent. The peak time, Tp, and the peak amplitude, D, of the activation current in nSW at 15.degree. C and -90 mV were 27 .+-. 4 s and -1.50 .+-. 0.47 nA, respectively. The currents through Na, Ca and anomalous K channels were evoked by test pulses with constant intervals in nSW and high-Sr, high-Ca and high-K ASW. Na-channel current was enhanced during activation. Ca-channel current decreased. In high-Ca, Na-free ASW the Ca current through Na channels increased while the Ca current through Ca channels decreased. The time for the maximum of Na current, Tmax, was (7.2 .+-. 1.5) .times. 10 s at 15.degree. C and index R, the ratio of the maximum amplitude to the amplitude before activation, was 2.31 .+-. 0.18 in nSW. The time for the minimum of Ca-channel current, Tmin, was .apprx. 70 s, being almost the same as Tmax of Na current. The current through anomalous K channels increased initially and decreased later with a time lag behind the decrease in Ca-channel current. Both Tp of activation current and Tmax of Na current were reduced by raising the temperature. Q10 for Tp and Tmax was 2.2 and 2.3, respectively. When the egg was activated in ASW containing scorpion toxin, the Na current through normal channels increased strongly while the Na current through toxin modified channels increased less markedly. There was no significant change in the tota membrane capacity before and during activation.