External and internal actions in the response of salamander retinal rods to altered external calcium concentration.
External and internal actions in the response of salamander retinal rods to altered external calcium concentration.
复制标题
蝾螈视网膜杆对外部钙浓度变化的反应的外部和内部作用。
DOI：
10.1113/jphysiol.1988.sp017259
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发表时间：
1988
期刊：
影响因子：
--
通讯作者：
Matthews,HR
中科院分区：
文献类型：
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作者：
Lamb,TD;Matthews,HR
1. 利用吸液移液管和全细胞膜片移液管技术记录了从虹膜上分离的视网膜棒的膜电流，同时外段的钙离子浓度迅速降低。2. 黑暗中外钙降低引起的外段电流增加可以分解为两个部分，一个与溶液变化的时间过程一样快（由结电流判断），另一个稍慢。3. 钙缓冲液BAPTA（1,2‐双（o‐氨基苯氧基）乙烷‐N，N,N′，N′‐四乙酸）从膜片移液器引入细胞导致电流增加的第二组分逐渐减慢。4. 当贴片破裂几分钟后，为了让大量的BAPTA进入细胞（在贴片移液管中约为10 mM），第二组分的速度减慢了约20倍，而第一组分的速度继续与溶液变化相同。5. 快速成分归因于外部钙，Ca2+o的直接作用，延迟成分归因于内部钙，Ca2+i减少介导的间接作用。6. 这些结果证实，在之前将BAPTA引入光感受器的实验中，内部钙浓度得到了非常显著的缓冲。7. 当Ca2+o从1 mM下降到小于10（‐8）M时，快速的外部成分对应于循环电流增加3 ~ 4倍，而内部成分对应于循环电流增加至少4 ~ 5倍。然而，后期的总电流受到电气因素的限制，因此内部效应的大小必然要大得多。
1. The membrane current was recorded from retinal rods isolated from Ambystoma tigrinum using the suction pipette and whole‐cell patch pipette techniques, while the concentration of calcium bathing the outer segment was rapidly reduced. 2. The increase in outer segment current induced by lowered external calcium in darkness could be resolved into two components, one as rapid as the time course of the solution change (as judged by the junction current) and the other somewhat slower. 3. Introduction of the calcium buffer BAPTA (1,2‐bis(o‐aminophenoxy)ethane‐N ,N ,N' ,N'‐tetraacetic acid) into the cell from a patch pipette led to a progressive slowing of the second component of current increase. 4. When several minutes had elapsed following rupture of the patch, to allow a substantial amount of BAPTA into the cell (ca. 10 mM in the patch pipette), the second component was slowed by a factor of about 20‐fold, while the first component continued to have the same rapid time course as the solution change. 5. The rapid component is attributed to a direct effect of external calcium, Ca2+o, and the delayed component to an indirect effect mediated by a reduction in internal calcium, Ca2+i. 6. These results confirm that, in previous experiments in which BAPTA was introduced into photoreceptors, the internal calcium concentration was very significantly buffered. 7. When Ca2+o drops from 1 mM to less than 10(‐8) M, the rapid external component corresponds to an increase in circulating current of 3‐ to 4‐fold, and the internal component corresponds to an increase of at least 4‐ to 5‐fold. However, the total current at late times is limited by electrical factors, so that the size of the internal effect is bound to be considerably greater.