title: Inward rectifier produced by Xenopus oocytes injected with mRNA extracted from carp olfactory epithelium.
abstract: Ionic channels encoded by mRNA extracted from carp olfactory epithelium were investigated by injection into Xenopus laevis oocytes. The oocytes expressed an inward rectifier K+ -channel, as detected under two-electrode voltage clamp conditions. The results were as follows. An inactivating inward current appeared on hyperpolarization and increased with increasing extracellular K+ concentrations. The 0 current potentials plotted as a function of log [K+]0 in the range between 2 to 20 mMK+ fell on a straight line, with a slope of 58 mV per tenfold change in K+ concentration, indicating that the current carrier is K+. Chord conductances reached saturation levels on extreme hyperpolarization. The chord conductances at the saturation levels were 35.7, 22.5, and 13.4 muSec in 20, 10, and 5 mM extracellular K+, respectively. Extracellular application of 0.1 mM Cs+ or 0.1 mM Ba2+ blocked the inward current in 2 mM K+, whereas 1 microM TTX or 0.3 mM Cd2+ did not affect the inward current. Inactivation of the inward currents, which became clear on extreme hyperpolarization, was suppressed with decreasing extracellular Na+ concentration. The present results suggest that carp olfactory epithelium is rich in the inward rectifier and is an excellent source of mRNA for cloning cDNA coding the inward rectifier.
authors.affiliation: Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Yoshii
authors.forename: K
authors.initials: K
authors.lastname: Kurihara
mesh_terms: D000818:Animals; D002347:Carps; D004553:Electric Conductivity; D004847:Epithelial Cells; D005260:Female; D009830:Olfactory Bulb / Q000166:cytology*; D009865:Oocytes / Q000502:physiology*; D015221:Potassium Channels / Q000502:physiology; D012333:RNA, Messenger / Q000502:physiology; D015222:Sodium Channels / Q000502:physiology; D013779:Tetrodotoxin / Q000494:pharmacology; D014982:Xenopus laevis
chemical_list: D015221:Potassium Channels; D012333:RNA, Messenger; D015222:Sodium Channels; D013779:Tetrodotoxin