Effects of transmembrane gradients of bicarbonate and ammonium on junctional and nonjunctional membrane conductances in BHK cells.

Weak acids are efficient blockers of gap-junctional conductance. It is generally accepted that intracellular acidification produced by weak acids fully accounts for the gap-junctional uncoupling. Protonation of the cytoplasmic portions of the channel-forming protein connexin is thought to lead to the conformational changes switching the channel from the open into the closed state.

Hemagglutinin-induced fusion of HAb2 and PLC cells: dynamics of fusion pore conductance.

Infection of cells with influenza virus is mediated by the virus envelope protein hemagglutinin (HA) which induces fusion of viral and target membranes. Earlier we showed using fluorescent microscopy that HAb2 cells expressing HA on their plasma membranes fused with PLC cells when pH of the external medium was decreased to -5. In the present work we used double whole-cell recording to monitor the intercellular conductance in HAb2/PLC cell pairs during fusion.

pH dependence of junctional conductance.

Current views on the molecular mechanisms of the pH dependence of gap junctions are mainly based on the experimental fact that extracellularly applied CO2 or other weak acids rapidly and reversibly block junctional conductance and also decrease intracellular pH. Data are presented suggesting that the mechanism of the uncoupling action of weak acids may be restricted to intracellular acidification. Hypotheses concerning possible protonation sites in the connexin molecules are also considered.

The effect of arachidonic acid on junctional conductance in isolated murine hepatocytes.

Arachidonic acid (AA) is known to inhibit intercellular conductance in normal and tumour cells. We showed that junctional conductance (Gj) in isolated murine hepatocytes was relatively tolerant to the uncoupling effect of AA. Extracellular application of 100 microM AA decreased Gj in less than 50% of hepatocytes, and the effect was much slower in other cells (10-15 min vs.