Non-electrolyte transport in brush border membrane vesicles from bovine small intestine
Moe, Aaron J.
MetadataShow full item record
Transport properties of bovine intestinal brush border membranes were investigated. Isolation of brush border membrane vesicles involved magnesium precipitation followed by a sucrose density gradient. Characterization by alkaline phosphatase activity (the brush border marker enzyme) showed 7 fold enrichment over homogenate at the interface between 38 and 42% sucrose. This fraction was employed to study transport of sugars and amino acids. Transport of D-glucose into an osmotically active space, was sodium stimulated, and inhibited by phloridzin, D-galactose, and D-xylose. Transport of L-alanine was sodium stimulated and mediated by at least two systems. Apparent affinities for L-alanine transport were .039, and .943 mM. Maximum velocities were 29.2, and 53.4 pmoles/mg protein/sec, for the two systems. Transport of L-proline, L-lysine, L-methionine, and L-phenylalanine were sodium stimulated. Data indicated sodium independent transport accounted for more influx of L-lysine, L-methionine, and L-phenylalanine than sodium dependent transport. Sodium dependent and sodium independent fluxes were equal for uptake of L-proline. Amino acid inhibition data indicated a common transporter for methionine, alanine, and phenylalanine. There was an additional methionine transport system not shared by alanine or phenylalanine. None of the amino acids effectively inhibited methionine uptake. Data indicated praline was transported by system(s) not shared by the other amino acids. Bovine brush border membranes transported the amino acid analog alpha-methyl-aminoisobutyric acid by sodium stimulated processes.
- Doctoral Dissertations