Calcium-sensitivity of the plasmalemmal delayed rectifier potassium current suggests that calcium influx in pulvinar protoplasts from Mimosa pudica L. can be revealed by hyperpolarization |
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Authors: | H Stoeckel K Takeda |
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Institution: | (1) Institut de Biologie Moléculaire des Plantes-CNRS UPR406, 67084 Strasbourg, France;(2) Université Louis Pasteur de Strasbourg, Laboratoire de Pharmacologie Cellulaire et Moléculaire-CNRS URA600, B.P. 24, 67401 Illkirch, France |
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Abstract: | Isolated protoplasts from pulvinar motor cells of Mimosa pudica were studied using conventional whole-cell patch clamp techniques. With internal solutions weakly buffered for Ca2+ (0.2 mm EGTA), a run-down of the outward delayed rectifier K+ current was induced by hyperpolarizing the holding potential, and this effect was strongly promoted by high external Ca2+ concentrations. This rundown could be reversed by coming back to less hyperpolarized holding potentials or by lowering the external Ca2+]. Such rundown was absent when pipette internal solutions strongly buffered (10 mm EGTA) for Ca2+ were used. Ionomycin induced run-down of the K+ current with internal solutions containing 0.2 mm but not 10 mm EGTA. The hyperpolarization-associated rundown was reversibly blocked by Gd3+ and La3+.We thank Christophe Untereiner and Denis Wagner for expert technical assistance in facilitating the experiments and data acquisition and analysis. |
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Keywords: | Mimosa pudica Pulvinus Protoplast Delayed rectifier potassium current Calcium influx Gadolinium |
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