Cl transport in the frog cornea: an electron-microprobe analysis.

Area of Science:

• Physiology
• Biophysics
• Cell Biology

Background:

• Understanding intracellular electrolyte concentrations is crucial for comprehending epithelial transport.
• Previous studies established ion activities in bullfrog corneal epithelium under open-circuit conditions.

Purpose of the Study:

• To determine intracellular electrolyte concentrations (Na, Cl, K) in bullfrog corneal epithelium using electron-microprobe analysis.
• To investigate ion transport mechanisms across the corneal epithelium.
• To explore the relationship between intracellular chloride and bicarbonate/CO2 levels.

Main Methods:

• Analysis of thin freeze-dried cryosections of bullfrog corneal epithelium.
• Utilized electron-microprobe analysis for precise intracellular ion concentration measurements.
• Corneal tissues were incubated in Conway's solution under short-circuited conditions.

Main Results:

• Mean intracellular concentrations: 8.0 mmol/kg for Na, 18.4 mmol/kg for Cl, and 117.3 mmol/kg for K.
• Identical chloride concentrations across epithelial layers suggest a functional syncytium.
• Evidence supports passive chloride efflux (apical) and Na-coupled chloride uptake (basolateral).

Conclusions:

• Intracellular electrolyte concentrations align with previously reported ion activities.
• Results suggest a passive electrodiffusive chloride efflux and Na-coupled chloride uptake mechanism.
• Intracellular chloride levels are influenced by bicarbonate and CO2, with potential complexities in chloride uptake mechanisms.