Single-channel events and gating behavior of the cardiac gap junction channel.

AUTOR(ES)

Burt, J M

RESUMO

The activity of gap junction channels between pairs of neonatal rat heart cells in culture was studied under control conditions and during uncoupling procedures by using dual whole-cell voltage clamp techniques. Under control conditions gap junctional conductance ranged from 0.05 to 35 nS. In cell pairs exhibiting low gap junctional conductance (less than 500 pS), single-channel events with a unitary conductance of 53 +/- 2 pS (5 experiments; 186 events) were apparent. Event duration and open-time probability were estimated to be 0.95 sec and 0.17, respectively. When the junctional conductance in well-coupled cell pairs (with initial junctional conductance, greater than 5 nS) was reduced by cytoplasmic acidification or application of heptanol, single-channel events could be visualized. Compared to low-conductance controls, unitary channel conductance was unaltered (for acidification the conductance was 58 +/- 3 pS in 11 experiments with 253 events; for heptanol the conductance was 61 +/- 1 pS in 2 experiments with 171 events), while the probability of channels being open was decreased. The constancy of unitary channel conductance under control conditions and during uncoupling procedures suggests that opening and closing of the gap junction channel are all-or-none processes during which no stable subconductance states are formed.

Documentos Relacionados

• Single-channel properties of a rat brain endoplasmic reticulum anion channel.
• Fast single-channel measurements resolve the blocking effect of Cs+ on the K+ channel.
• Horizontal cell gap junctions: single-channel conductance and modulation by dopamine.
• A helical-dipole model describes the single-channel current rectification of an uncharged peptide ion channel.
• Diffusion models of ion-channel gating and the origin of power-law distributions from single-channel recording.