Ion channel activity from the midgut brush-border membrane of gypsy moth (Lymantria dispar) larvae.
Ion channels from the midgut apical membrane of gypsy moth (Lymantria dispar) larvae were studied following mechanical fusion of brush-border membrane vesicles with planar phospholipid bilayer membranes. In symmetrical 300 mmol l(-)(1) KCl (pH 9.0), nine different channels with conductances ranging from 27 to 795 pS and linear current/voltage relationships were resolved. In the presence of a KCl gradient across the bilayer (450 mmol l(-)(1 )cis/150 mmol l(-)(1 )trans), 11 different conductance levels ranging from 16 to 850 pS were detected. The channels were slightly cationic: the zero-current reversal potential was shifted by -5 mV to -21 mV compared with symmetrical KCl conditions, corresponding to p(K)/p(Cl) permeability ratios of 1.5-8.0. Most channels were neither voltage-dependent nor Ca(2+)-sensitive and displayed complex gating kinetics. Addition of Ba(2+) or Cs(+) to both sides of the bilayer had little effect on channel activity, but fewer distinct channels were observed when KCl was replaced by potassium gluconate, suggesting an effect of Cl(-) on channel activity. A reduced number of channels was also detected when KCl was replaced by N-methyl-d-glucamine-HCl. Under asymmetrical N-methyl-d-glucamine-HCl conditions, only anionic channels were observed. They exhibited current rectification (35 pS at negative voltages and 81 pS at positive voltages) and were strongly voltage-dependent.
Peyronnet
O
O
Groupe de Recherche en Transport Membranaire, Université de Montréal, Quebec, Canada.
Vachon
V
V
Schwartz
J L
JL
Laprade
R
R
D000818:Animals; D000838:Anions; D001464:Barium / Q000494:pharmacology; D002586:Cesium / Q000494:pharmacology; D004553:Electric Conductivity; D005942:Gluconates / Q000494:pharmacology; D007422:Intestines; D007473:Ion Channels / Q000502:physiology*; D008051:Lipid Bilayers / Q000378:metabolism; D008536:Meglumine / Q000494:pharmacology; D008561:Membrane Fusion; D008871:Microvilli / Q000502:physiology; D009036:Moths / Q000502:physiology*; D011189:Potassium Chloride / Q000494:pharmacology
D000838:Anions; D005942:Gluconates; D007473:Ion Channels; D008051:Lipid Bilayers; D002586:Cesium; D001464:Barium; D011189:Potassium Chloride; D008536:Meglumine; C030691:gluconic acid