title: A calcium homeostasis mechanism induced by heterologous expression of total RNA from chicory leaves in Xenopus oocytes.
abstract: Xenopus oocytes were injected with total RNA from chicory leaf tissues and then examined by the voltage-clamp technique. A double-step voltage protocol was used, with an initial hyperpolarization step from the holding potential of -35 to -140 mV followed by a second depolarization step to +60 mV. Two different outward currents were observed, one noninactivating (Ini), and one inactivating (Ii). Only the noninactivating outward current (Ini) could be induced by depolarization from -35 to +60 mV. The mean amplitude of Ini was 2915 +/- 848 nA (n = 11). This current, carried by chloride ions, declined nearly to the baseline in 153 +/- 64 sec (n = 13), and was highly dependent on intracellular calcium. After the rundown of Ini, the same oocyte was depolarized from -140 to +60 mV. This protocol induced an inactivating outward current (Ii) with a mean amplitude of 4461 +/- 1605 nA (n = 13). Ii was also carried by chloride ions and dependent on extracellular calcium. Ii was strongly inhibited by 100 micron extracellular La3+. These two types of chloride currents were also observed after IP3 injection in control oocytes. Ini and Ii were not observed in noninjected oocytes or water-injected oocytes. We suggest that the expression of total chicory leaf tissue RNA in Xenopus oocytes reveals a calcium homeostasis mechanism responsible for calcium mobilization from internal stores and subsequent calcium entry.
authors.affiliation: Laboratoire de Physiologie Cellulaire, SN3, Université des Sciences et Technologie de Lille, 59655 Villeneuve d'Ascq Cedex, France.
authors.forename: M
authors.initials: M
authors.lastname: Debarbieux
authors.forename: H
authors.initials: H
authors.lastname: Ouadid-Ahidouch
authors.forename: N
authors.initials: N
authors.lastname: Delpierre
authors.forename: J
authors.initials: J
authors.lastname: Vasseur
authors.forename: N
authors.initials: N
authors.lastname: Prevarskaya
mesh_terms: D000818:Animals; D002118:Calcium / Q000502:physiology*; D018651:Cichorium intybus / Q000235:genetics*; D018118:Chloride Channels / Q000235:genetics; D004594:Electrophysiology; D015870:Gene Expression; D006706:Homeostasis; D009865:Oocytes; D018515:Plant Leaves / Q000235:genetics*; D012313:RNA / Q000235:genetics; D014981:Xenopus
chemical_list: D018118:Chloride Channels; D012313:RNA; D002118:Calcium