Electrical properties of gap junction channels in guinea-pig ventricular cell pairs revealed by exposure to heptanol.
Cell pairs were isolated from adult guinea pig ventricles to study the electrical properties of gap junction channels. The experiments involved a double voltage-clamp approach and whole-cell, tight-seal recording. Heptanol decreased the intracellular current, In, in a dose-dependent fashion. Before complete uncoupling, In showed fluctuations suggesting the operation of gated channels. In the presence of 3 mM heptanol, In showed quantal steps arising from spontaneous opening and closing of single channels. The IV-relationship of the channels was linear (range: +/- 95 mV). Analysis of current records revealed the following single-channel conductances, gamma n: Mean value = 37 pS; median value = 33 pS. gamma n was insensitive to the non-junctional membrane potential (range: -90 to +10 mV). 3 mM ATP4- in the pipette solution had no effects on gamma n, 6 mM ATP4- produced a small decrease, and 6 mM ATP + 0.1 mM cAMP- an increase in gamma n. Channel transitions from closed to open state were variable (range of apparent time constants: 2.5-32 ms; mean: 11 ms).
Rüdisüli
A
A
Department of Physiology, University of Berne, Switzerland.
Weingart
R
R
D000438:Alcohols / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004533:Egtazic Acid / Q000494:pharmacology; D004553:Electric Conductivity; D006168:Guinea Pigs; D006352:Heart Ventricles / Q000648:ultrastructure; D019850:Heptanol; D007365:Intercellular Junctions / Q000187:drug effects / Q000502:physiology*; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D008564:Membrane Potentials / Q000502:physiology; D009206:Myocardium / Q000648:ultrastructure*
D000438:Alcohols; D007473:Ion Channels; D004533:Egtazic Acid; D019850:Heptanol; D002118:Calcium