title: Voltage-dependent potassium currents expressed in Xenopus laevis oocytes after injection of mRNA isolated from trophozoites of Giardia lamblia (strain Portland-1).
abstract: Despite its importance as a health problem issue, almost nothing is known about the membrane physiology of Giardia lamblia and practically there exist no information so far regarding the variety and properties of ion channels that this protozoan parasite possesses. To address this subject we resorted to an indirect method, consisting in the injection of mRNA and further characterization of ion currents in Xenopus oocytes. In this work, we show that oocytes injected with mRNA isolated from cultured trophozoites of G. lamblia, strain Portland-1 express novel potassium currents that appear over the second day after injection and show time- and voltage-dependent activation followed by a slow inactivation. They start activating at -90 mV, with V1/2 of -30 mV; its time constant of activation (at +60 mV) is 0.11 sec, whereas that of inactivation is 1.92 sec, V1/2 = -44.6 mV. Such K currents were effectively blocked by K channel blockers TEA and 4AP, as well as Ba(2+), quinine, quinidine, charybdotoxin, dendrotoxin-1, capsaicin, margatoxin, and diltiazem. These results suggest that such currents are the result of expression of Giardia's voltage-gated K channels heterologously expressed in Xenopus laevis oocytes.
authors.affiliation: Department of Physiology, Biophysics and Neurosciences, Center for Research and Advanced Studies IPN, México City, Mexico.
authors.forename: Arturo
authors.initials: A
authors.lastname: Ponce
authors.affiliation: Parasitology Research Laboratory, Children Hospital of México "Federico Gomez", Mexico City, México.
authors.forename: Enedina
authors.initials: E
authors.lastname: Jimenez-Cardoso
authors.affiliation: Parasitology Research Laboratory, Children Hospital of México "Federico Gomez", Mexico City, México.
authors.forename: Leticia
authors.initials: L
authors.lastname: Eligio-Garcia
keywords: Giardia lamblia; K currents; Xenopus oocytes; voltage clamp
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