Electrogenic Na+/HCO3- cotransport in neuroglia.

Area of Science:

• Neuroscience
• Cell Physiology
• Biochemistry

Background:

• Glial cells play crucial roles in the central nervous system.
• Understanding ion transport mechanisms in glial cells is vital for comprehending neural function.
• Previous studies suggested potential involvement of bicarbonate transporters in glial cells.

Purpose of the Study:

• To investigate the presence and characteristics of a sodium/bicarbonate cotransporter in Necturus optic nerve glial cells.
• To determine the stoichiometry and electrogenic nature of the identified transporter.

Main Methods:

• Membrane potential recordings were performed on glial cells from Necturus optic nerve.
• Experiments involved manipulating extracellular sodium (Na+) and bicarbonate (HCO3-) concentrations.
• Potassium (K+) conductance was blocked using barium ions (Ba++).
• The effect of 4-acetamido-4'-isothiocyanato-stilbene-2,2'-disulfonic acid (SITS) on bicarbonate transport was assessed.

Main Results:

• Reducing extracellular Na+ in the presence of HCO3- caused significant depolarization, more so than in HCO3--free solutions.
• Removal of HCO3- greatly diminished the hyperpolarizing effect of adding HCO3- in low Na+ solutions.
• SITS, a known stilbene derivative, inhibited the HCO3- mediated effects, suggesting a role for stilbene-sensitive transporters.

Conclusions:

• The results strongly indicate the presence of an electrogenic Na+/HCO3- cotransporter in the glial membrane.
• The data suggest a stoichiometry where the transporter moves more HCO3- ions relative to Na+ ions.
• This Na+/HCO3- cotransporter likely plays a significant role in regulating glial cell membrane potential and intracellular pH.