Single K+ channels in endocrine cells dispersed from the cricket (Gryllus bimaculatus) corpora allata.
Single channel currents were recorded from cell-attached patches of endocrine cells of the adult male cricket corpora allata. Three distinct types of K+ channels were identified; a weak inward rectifier (Type 1), a strong inward rectifier (Type 2) and a weak outward rectifier (Type 3). The type 1 channel had a slope conductance of 191 +/- 9 pS (n = 4) at negative membrane potentials (Vm) and 101 +/- 6 pS (n = 6) at positive Vm. In addition, the channel showed fast open-closed kinetics at negative Vm and slow open-closed kinetics at positive Vm. The open probability (Po) of this channel was strongly voltage-dependent at positive Vm, but less voltage-dependent at negative Vm. The reversal potential was not modified significantly by the substitution of gluconate for external Cl- but was modified after N-methyl-D-glucamine (NMDG+) was substituted for external K+, according to the Nernst equation for a K+-selective channel. The type 2 channel had a slope conductance of 44 +/- 2 pS (n = 5) at negative Vm, but no detectable outward current was observed at positive Vm. This channel showed very slow open-closed kinetics at negative Vm and its Po was not voltage-dependent. The type 3 channel had a limit conductance of 55 +/- 12 pS (n = 3) at negative Vm and 88 +/- 10 pS (n = 3) at positive Vm. This channel showed slow open-closed kinetics at negative Vm and fast open-closed kinetics at positive Vm. The Po for the channel was voltage-dependent at positive Vm but was voltage-independent at negative Vm. These three types of K+ channels may be important for the control of the resting membrane potential, and may thus participate in the regulation of Ca2+ influx and juvenile hormone secretion in corpora allata cells.
Kosakai
K
K
Department of Biology, Tokyo Gakugei University, Japan.
Yoshino
M
M
D000818:Animals; D002712:Chlorides / Q000494:pharmacology; D003335:Corpora Allata / Q000166:cytology / Q000502:physiology; D005942:Gluconates / Q000494:pharmacology; D006135:Gryllidae / Q000502:physiology*; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D008297:Male; D008536:Meglumine / Q000031:analogs & derivatives* / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000493:pharmacokinetics; D024661:Potassium Channels, Inwardly Rectifying / Q000502:physiology*
D002712:Chlorides; D005942:Gluconates; D024661:Potassium Channels, Inwardly Rectifying; C051643:N-methylglucamine gluconate; D008536:Meglumine; D011188:Potassium