TY - JOUR
T1 - Inactivation of calcium-activated chloride conductance in Xenopus oocytes
T2 - roles of calcium and protein kinase C
AU - Boton, Rony
AU - Singer, Dafna
AU - Dascal, Nathan
PY - 1990/4
Y1 - 1990/4
N2 - Inactivation of Ca2+ -induced Cl- currents was studied in Xenopus oocytes using the two-electrode voltage-clamp technique. In oocytes permeabilized to Ca2+ by treatment with the ionophore A23187, Ca2+ influx caused by the addition of 2.5-5 mM Ca2+ to the extracellular solution elicited Cl- currents consisting of two components: a fast, transient one (Ifast) and a slow one (Islow). In response to a subsequent application of the same dose of Ca2+, Ifast and Islow were reduced (inactivation phenomenon). The inactivation did not depend on the direction of current flow, but did depend on the duration of the first exposure to Ca2+. The extent of inactivation of Ifast was more significant than that to Islow. Both Ifast and Islow fully recovered from inactivation in less than 30 min. Intracellular injections of 100-400 pmol CaCl2 evoked large inward currents but did not reduce the amplitude of currents evoked by Ca2+ influx. The activator of protein kinase C, β-phorbol dibutyrate, caused full inhibition of Ifast without any change in Islow. H-7 (1,5-isoquinolinesulfonyl-1,2 methylpiperazine), an inhibitor of protein kinases, strongly reduced the extent of inactivation. Our results suggest that elevation of intracellular Ca2+ by Ca2+ influx through the plasma membrane causes inactivation of the Ca2+ -dependent Cl- conductance via activation of a Ca2+ -dependent protein kinase, possibly protein kinase C, whereas Ca2+ arriving at the membrane from inside the cell does not initiate the processes leading to inactivation.
AB - Inactivation of Ca2+ -induced Cl- currents was studied in Xenopus oocytes using the two-electrode voltage-clamp technique. In oocytes permeabilized to Ca2+ by treatment with the ionophore A23187, Ca2+ influx caused by the addition of 2.5-5 mM Ca2+ to the extracellular solution elicited Cl- currents consisting of two components: a fast, transient one (Ifast) and a slow one (Islow). In response to a subsequent application of the same dose of Ca2+, Ifast and Islow were reduced (inactivation phenomenon). The inactivation did not depend on the direction of current flow, but did depend on the duration of the first exposure to Ca2+. The extent of inactivation of Ifast was more significant than that to Islow. Both Ifast and Islow fully recovered from inactivation in less than 30 min. Intracellular injections of 100-400 pmol CaCl2 evoked large inward currents but did not reduce the amplitude of currents evoked by Ca2+ influx. The activator of protein kinase C, β-phorbol dibutyrate, caused full inhibition of Ifast without any change in Islow. H-7 (1,5-isoquinolinesulfonyl-1,2 methylpiperazine), an inhibitor of protein kinases, strongly reduced the extent of inactivation. Our results suggest that elevation of intracellular Ca2+ by Ca2+ influx through the plasma membrane causes inactivation of the Ca2+ -dependent Cl- conductance via activation of a Ca2+ -dependent protein kinase, possibly protein kinase C, whereas Ca2+ arriving at the membrane from inside the cell does not initiate the processes leading to inactivation.
KW - Chloride channel
KW - Inactivation
KW - Protein kinase C
KW - Xenopus oocyte
UR - http://www.scopus.com/inward/record.url?scp=0025347251&partnerID=8YFLogxK
U2 - 10.1007/BF00370214
DO - 10.1007/BF00370214
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AN - SCOPUS:0025347251
SN - 0031-6768
VL - 416
SP - 1
EP - 6
JO - Pflugers Archiv European Journal of Physiology
JF - Pflugers Archiv European Journal of Physiology
IS - 1-2
ER -