ISSN:
1615-6102
Keywords:
Ca2+ channel
;
Cl− channel
;
K+ channel
;
Patch clamp
;
Tobacco culture cell
;
Vacuole
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Summary K+, Cl−, and Ca2+ channels in the vacuolar membrane of tobacco cell suspension cultures have been investigated using the patch-clamp technique. In symmetrical 100mM K+, K+ channels opened at positive vacuolar membrane potentials (cytoplasmic side as reference) had different conductances of 57 pS and 24 pS. K+ channel opened at negative vacuolar membrane potentials had a conductance of 43 pS. The K+ channels showed a significant discrimination against Na+ and Cl−. The Cl− channel opened at positive vacuolar membrane potentials for cytoplasmic Cl− influx had a high conductance of 110pS in symmetrical 100mM Cl−. When K+ and Cl− channels were excluded from opening, no traces were found of Ca2+ channel activity for vacuolar Ca2+ release induced by inositol 1,4,5-trisphosphate or other events. However, we found a 19pS Ca2+ channel which allowed influx of cytoplasmic Ca2+ into the vacuole when the Ca2+ concentration on the cytoplasmic side was high. When Ca2+ was substituted by Ba2+, the conductance of the 19 pS channel became 30 pS and the channel showed a selectivity sequence of Ba2+∶Sr2+∶Ca2+∶Mg2+=1∶0.6∶0.6∶0.21. The reversal potentials of the channel shifted with the change in Ca2+ concentration on the vacuolar side. The channel could be efficiently blocked from the cytoplasmic side by Cd2+, but was insensitive to La3+, Gd3+, Ni2+, verapamil, and nifedipine. The related ion channels in freshly isolated vacuoles from red beet root cells were also recorded. The coexistence of the K+, Cl−, and Ca2+ channels in the vacuolar membrane of tobacco cells might imply a precise classification and cooperation of the channels in the physiological process of plant cells.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01379275
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