title: Resolution of apical from basolateral membrane of shark rectal gland.
abstract: Membrane fractions were isolated from the rectal gland of Squalus acanthias using differential centrifugation and a sucrose gradient run in the presence of 1 M KBr. Using the basolateral membrane marker Na+-K+-ATPase, we obtained a sixfold purification with the most highly purified fraction from the gradient (sp act = 336 +/- 37 mumol X mg protein-1 X h-1). Electrogenic Br- transport was used as a marker activity of the apical membrane, which enabled the identification and purification of a membrane fraction that is highly resolved from the basolateral membrane. The most active fraction was purified approximately 50-fold compared with the crude homogenate. In this fraction, the specific activity of electrogenic anion transport was 296 +/- 87 nmol X mg protein-1 X min-1, whereas the ATPase was only 17.6 +/- 5.7 mumol X mg protein-1 X h-1, representing about a 4-5% contamination of the apical fraction with the basolateral membrane.
mesh_terms: D000818:Animals; D000838:Anions; D001692:Biological Transport; D001965:Bromides / Q000378:metabolism; D002458:Cell Fractionation; D002462:Cell Membrane / Q000378:metabolism / Q000648:ultrastructure; D002463:Cell Membrane Permeability; D002499:Centrifugation, Density Gradient; D002712:Chlorides / Q000378:metabolism; D004284:Dogfish / Q000033:anatomy & histology*; D004553:Electric Conductivity; D012491:Salt Gland / Q000378:metabolism / Q000648:ultrastructure*; D012754:Sharks / Q000033:anatomy & histology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
chemical_list: D000838:Anions; D001965:Bromides; D002712:Chlorides; D000254:Sodium-Potassium-Exchanging ATPase