Octanol, a gap junction uncoupling agent, changes intracellular [H+] in rat astrocytes

Area of Science:

• Neuroscience
• Cell Biology
• Biochemistry

Background:

• Octanol is known to rapidly close gap junction channels.
• The precise mechanism by which octanol affects gap junction conductance remains unclear.
• Intracellular pH (pHi) is a known regulator of gap junction channel conductance.

Purpose of the Study:

• To investigate the effects of octanol on intracellular pH (pHi) in cultured rat astrocytes.
• To elucidate the mechanisms underlying octanol-induced changes in astrocytic pHi.
• To determine the relationship between octanol-induced pHi alterations and gap junction coupling in astrocytes.

Main Methods:

• Cultured rat hippocampal astrocytes were used to study octanol's effects on pHi.
• Changes in pHi were monitored using pH-sensitive dyes.
• Na+/HCO3- cotransport and Na+/H+ exchanger (NHE) activity were assessed using specific inhibitors (DIDS and amiloride, respectively).
• Gap junction coupling was evaluated using fluorescence recovery after photobleaching (FRAP).

Main Results:

• Octanol (1 mM) induced an average acid shift of -0.19 pH units in 90% of astrocytes.
• A biphasic pHi change (acidification followed by alkalinization) was observed in 58% of cells.
• Octanol-induced acidification was mediated by inhibition of Na+/HCO3- cotransport, while alkalinization involved stimulation of NHE.
• External Na+ removal abolished octanol's effects on pHi.
• Intracellular acidification significantly decreased gap junction coupling in astrocytes.

Conclusions:

• Octanol exerts complex effects on astrocytic pHi, involving inhibition of acid extrusion and stimulation of another.
• The initial acidification caused by octanol can contribute to its gap junction uncoupling effect in astrocytes.
• Octanol can influence gap junctional conductance independently of pHi changes, as evidenced by its effects on hepatocytes.