Disaccharide uptake by brush-border membrane vesicles lacking the corresponding hydrolases.

Area of Science:

• Gastroenterology
• Molecular Biology
• Cell Biology

Background:

• Intestinal disaccharide digestion and absorption are critical for nutrient utilization.
• Brush-border membrane vesicles (BBMVs) are essential tools for studying nutrient transport.

Purpose of the Study:

• To investigate the mechanism of intestinal disaccharide uptake.
• To determine if intact disaccharides are transported across the brush-border membrane.

Main Methods:

• Isolated brush-border membrane vesicles (BBMVs) from chick and pig intestines were used.
• Vesicles lacked specific disaccharidases (trehalase, lactase, sucrase).
• Uptake of disaccharides (lactose, trehalose, sucrose) was measured and compared to diffusion markers (D-mannitol, L-glucose).

Main Results:

• Disaccharide uptake rates were indistinguishable from diffusion markers.
• Uptake was not affected by Na+, phlorizin, or Tris, indicating no active transport.
• Chromatographic analysis confirmed no disaccharide hydrolysis within vesicles.

Conclusions:

• Intact disaccharides do not undergo active transport across the intestinal brush-border membrane.
• Disaccharide uptake occurs primarily through simple diffusion.
• This finding challenges previous assumptions about disaccharide absorption mechanisms.