Bicarbonate and DIDS effects on intracellular potential difference in rabbit ciliary epithelium

Area of Science:

• Physiology
• Cell Biology
• Ocular Science

Background:

• The ciliary epithelium plays a crucial role in aqueous humor production and intraocular pressure regulation.
• Bicarbonate ions ([HCO3-]) are known to influence cellular functions, including electrical potential differences.

Purpose of the Study:

• To investigate the effect of varying extracellular bicarbonate concentrations on the intracellular electrical potential difference (PDI) of isolated rabbit ciliary epithelium.
• To explore the potential involvement of bicarbonate transport mechanisms in regulating PDI.

Main Methods:

• Isolated rabbit ciliary epithelium was bathed in solutions with varying bicarbonate concentrations (0 mM to 30 mM).
• Intracellular electrical potential difference (PDI) was measured using microelectrode techniques.
• The effects of the stilbene derivative 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) were assessed.

Main Results:

• A decrease in [HCO3-] from 30 mM to 0 mM caused a 7 mV depolarization of PDI.
• PDI showed a gradual depolarization with decreasing [HCO3-] and a faster hyperpolarization with increasing [HCO3-].
• DIDS induced hyperpolarization in bicarbonate-rich solutions, with reduced effects in bicarbonate-free or chloride-free solutions.

Conclusions:

• The results strongly suggest the presence of an electrogenic bicarbonate transport system in the rabbit ciliary epithelium.
• Evidence supports the involvement of a Na+/HCO3- cotransport system in regulating PDI.
• These findings contribute to understanding the physiological mechanisms governing ocular fluid dynamics.