Erythrocyte permeability to lipophilic solutes changes with temperature

Area of Science:

• Biophysics
• Cell Biology
• Physical Chemistry

Background:

• Understanding biological barrier permeability is crucial for drug delivery and toxicology.
• Homologous series studies offer insights into membrane characteristics.

Purpose of the Study:

• To determine permeability coefficients and activation energies for various solutes across dog erythrocyte membranes, hemoglobin, and plasma.
• To investigate the relationship between solute properties (lipid solubility, size) and membrane transport pathways.

Main Methods:

• Measurement of linear diffusion coefficients for tracer water (THO), [14C]antipyrine, [14C]acetamide, and n-[14C]alcohols.
• Calculation of permeability coefficients (Po) using the series-parallel pathway model.
• Determination of apparent activation energies (Ea) for permeability.

Main Results:

• Permeability coefficients varied significantly among solutes and barriers.
• Alcohols generally showed higher permeability than water, except for hexanol.
• Acetamide and antipyrine exhibited considerably lower permeability than water.
• Apparent activation energies indicated distinct transport mechanisms for small polar molecules versus larger lipid-soluble ones.

Conclusions:

• Erythrocyte membranes display heterogeneity in solute-membrane interactions and transport pathways.
• Both lipid solubility and solute size are critical factors influencing the transport of lipid-soluble molecules.
• Findings support a model of complex membrane dynamics affecting molecular permeation.