title: Na+-dependent transport of alpha-aminoisobutyrate in isolated basolateral membrane vesicles from rat parotid glands.
abstract: Basolateral plasma membranes were prepared from rat parotid gland after centrifugation in a self-orienting Percoll gradient. K+-dependent phosphatase [Na+ + K+)-ATPase), a marker enzyme for basolateral membranes, was enriched 10-fold from tissue homogenates. Using this preparation, the transport of alpha-aminoisobutyrate was studied. The uptake of alpha-aminoisobutyrate was Na+-dependent, osmotically sensitive, and temperature-dependent. In the presence of a Na+ gradient between the extra- and intravesicular solutions, vesicles showed an 'overshoot' accumulation of alpha-aminoisobutyrate. Sodium-dependent alpha-aminoisobutyrate uptake was saturable, exhibiting an apparent Km of 1.28 +/- 0.35 mM and Vmax of 780 +/- 170 pmol/min per mg protein. alpha-Aminoisobutyrate transport was inhibited considerably by monensin, but incubating with ouabain was without effect. These results suggest that basolateral membrane vesicles, which possess an active amino acid transport system (system A), can be prepared from the rat parotid gland.
mesh_terms: D000621:Aminoisobutyric Acids / Q000378:metabolism*; D000818:Animals; D001485:Basement Membrane / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism*; D002499:Centrifugation, Density Gradient; D007700:Kinetics; D008297:Male; D008985:Monensin / Q000494:pharmacology; D009994:Osmolar Concentration; D010042:Ouabain / Q000494:pharmacology; D010306:Parotid Gland / Q000166:cytology*; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism*
chemical_list: D000621:Aminoisobutyric Acids; C100049:2-aminoisobutyric acid; D010042:Ouabain; D008985:Monensin; D012964:Sodium