Electrical tolerance (breakdown) of theChara corallina plasmalemma: II. Inductive property of membrane and effects of pH
o
and impermeable monovalent cations on breakdown phenomenon |
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Authors: | Taka-aki Ohkawa Izuo Tsutsui |
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Institution: | (1) Department of Biology, College of General Education, Osaka University, 560 Toyonaka, Japan;(2) Cell Physiology, National Institute for Physiological Sciences, 444 Okazaki, Japan |
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Abstract: | Summary Changes in the chord conductanceG and the membrane electromotive forceE
m
in the so-called breakdown region of large negative potential of theChara plasmalemma were analyzed in more detail. In addition to the increase inG, the voltage sensitivity of the change inG increased, which was the cause of marked inductive current in the breakdown region. The breakdown potential, defined as a critical potential at which both low and high slope conductances of theI–V
m
relationship cross, almost coincided with the potential at which an inductive current began to appear. This breakdown potential level changed with pH
o
in a range between 5 and 9. TheChara plasmalemma was electrically most tolerant around pH
o
7.In some cellsE
m
shifted to a positive level as large as +50+70 mV during the breakdown phenomenon. Such a large positive shift ofE
m
is caused mainly by the increase in conductance of Cl– and partly Ca2+ and K+. |
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Keywords: | Chara DC conductance electrical tolerance electromotive force (E
m
) inductive property kinetics of Cl– channel |
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