Lung lamellar bodies maintain an acidic internal pH

Area of Science:

• Cell Biology
• Pulmonary Physiology
• Biochemistry

Background:

• Lung lamellar bodies are vital organelles in pulmonary surfactant production.
• Understanding their internal pH is key to understanding surfactant secretion and lung function.

Purpose of the Study:

• To investigate and quantify the internal pH of lung lamellar bodies.
• To determine the mechanisms responsible for maintaining this pH.

Main Methods:

• Utilized membrane-permeable fluorescent amines (quinacrine) to detect acidic pH.
• Measured [14C]methylamine uptake in isolated lamellar bodies to determine intralamellar pH.
• Assessed the effects of varying external conditions and chemical agents on pH gradients.

Main Results:

• Isolated lung lamellar bodies showed fluorescence with quinacrine, indicating an acidic interior.
• Methylamine uptake revealed an intralamellar pH of 6.1 in standard medium and 5.6 in K+-free medium.
• The pH gradient was sensitive to external pH, ATP presence, and specific ionophores/inhibitors.

Conclusions:

• Lung lamellar bodies actively maintain an acidic internal pH (≤ 6.1).
• This acidic environment is established via an energy-dependent mechanism.
• The findings provide insights into the biophysical properties of lamellar bodies relevant to lung physiology.