Na-dependent L-proline transport by eel intestinal brush-border membrane vesicles

Area of Science:

• Marine Biology
• Physiology
• Biochemistry

Background:

• The intestinal absorption of amino acids is crucial for nutrient acquisition in fish.
• Understanding the specific transport mechanisms for amino acids like L-proline in the European eel (Anguilla anguilla) is important for fish physiology and aquaculture.

Purpose of the Study:

• To investigate the mechanism of L-proline uptake by intestinal brush-border membrane vesicles of the European eel.
• To characterize the kinetics and stoichiometry of sodium-dependent L-proline transport.

Main Methods:

• Preparation of brush-border membrane vesicles from European eel intestinal mucosa.
• Measurement of L-[3H]proline uptake under varying sodium (Na) gradients and transmembrane potentials.
• Kinetic analysis (Michaelis-Menten) and Hill analysis to determine transport parameters and stoichiometry.
• Inhibition studies using specific amino acid transport system inhibitors.

Main Results:

• L-proline uptake was stimulated by a transmembrane Na gradient.
• A single apparent Na-dependent carrier process with specific kinetic parameters (Kapp, Jmax) and a nonsaturable component were identified.
• A 1:1 stoichiometry for Na-proline cotransport was determined via Hill analysis.
• Transmembrane potential influenced binding affinity but not maximal influx.
• Inhibitor studies suggested involvement of Na-dependent A, PHE, and IMINO transport systems.

Conclusions:

• The European eel intestine employs a Na-dependent cotransport system for L-proline.
• The transport mechanism appears to involve a 1:1 stoichiometry of sodium to proline.
• Multiple Na-dependent amino acid transport systems likely contribute to L-proline uptake in the eel intestine.