IONIC CONDUCTANCES OF SURFACE AND TRANSVERSE TUBULAR MEMBRANES OF FROG SARTORIUS FIBERS
IONIC CONDUCTANCES OF SURFACE AND TRANSVERSE TUBULAR MEMBRANES OF FROG SARTORIUS FIBERS
复制标题
DOI：
10.1085/jgp.53.3.279
复制
发表时间：
1969-01-01
影响因子：
3.8
通讯作者：
GAGE, PW
中科院分区：
文献类型：
--
作者：
EISENBERG, RS;GAGE, PW
测定了蛙缝匠肌纤维在不同条件下的静息离子电导率，以测定管状膜和表面膜的钾电导率（g~: t和gK′）和管状膜和表面膜的氯电导率（g~: t和gK′）。在正常纤维和无管纤维中，测量输入电阻和直径在正常pH值和低pH值下进行，此时氯离子电导非常小。这些测量允许离子电导的分离：gct'= 219# mhos/cm~；高尔夫-“0# mhos/cm~；gK"= 28/~ mhos/cm2；gkt = 55# rnhos/cm。讨论了系统误差的可能来源，并对随机误差的影响进行了统计分析。讨论了膜性质不均匀性的含义以及可能的解剖学解释。包裹蛙缝肌纤维肌质的膜由周向表面膜和膜的管状内陷（位于每个肌节的Z线）组成，它们构成横向管状系统。由于这两种体系的膜是连续的，所以人们可能会认为它们具有相似的性质，但一些证据表明并非如此。例如，细胞外氯离子浓度的突然变化所产生的膜电位变化比钾离子浓度的类似变化所产生的膜电位变化要快（Hodgkin和Horowicz， 1960）。对时间过程差异的一种解释是，与氯离子系统相比，钾离子电导系统更不易被溶液应用于纤维外部。如果钾离子电导系统仅位于横管中，而氯离子电导系统位于表面，那么钾离子浓度变化的响应显然会比氯离子浓度变化的响应慢。
The resting ionic conductances of frog sartorius muscle fibers have been determined in a variety of conditions in order to measure the potassium conductance of the tubular and surface membranes (g~: t and gK') and the chloride conductance of the tubular and surface membranes (got t and gore). In both normal fibers and fibers without tubules, measurements of input resistance and diameter were made at normal pH and at low pH when the chloride conductance was very small. These measurements permitted the separation of the ionic conductances: gct'= 219# mhos/cm~; golt-" 0# mhos/cm~; gK"= 28/~ mhos/cm2; gK t= 55# rnhos/cm. Possible sources of systematic error are discussed and a statistical analysis of the effects of random error is presented. The implications of the nonuniformity of membrane properties are discussed along with possible anatomical explanations.The membrane which encloses the sarcoplasm of frog sartorius fibers consists of the circumferential surface membrane and tubular invaginations of the membrane (located at the Z line in each sarcomere) which constitute the transverse tubular system. It might be expected that the membranes of both systems would have similar properties since they are continuous, but some evidence suggests otherwise. For example the change in membrane potential produced by a sudden change in the extracellular chloride concentration is faster than that produced by a similar change in potassium concentration (Hodgkin and Horowicz, 1960). One explanation for the difference in time course is that the potassium conductance system is less accessible to solutions applied to the outside of a fiber than is the chloride system. If the potassium conductance system were located only in the transverse tubules, while the chloride conductance system was on the surface, one clearly would expect the response to a change in potassium concentration to be slower than the response to a change in chloride concentration.