Enzyme activities and sodium-dependent active D-glucose transport in apical membrane vesicles isolated from kidney epithelial cell line (LLC-PK1).

Apical membrane vesicles were isolated from the confluent LLC-PK1 cells by nitrogen cavitation and Mg/EGTA precipitation methods. The specific activities of marker enzymes for apical membranes were enriched 8- to 18-fold relative to those in the homogenate. D-[3H]Glucose uptake into the vesicles was stimulated in the presence of Na+ gradient (overshoot phenomenon), and the values of apparent Km and Vmax for Na+-dependent component of D-glucose uptake were 0.3 mM and 5.8 nmol/mg protein per min, respectively.