title: A map of membrane populations isolated from rat exorbital gland.
abstract: We combined separation procedures based on three independent physical properties, sedimentation coefficient, density, and partitioning in an aqueous polymer two-phase system, to generate a three-dimensional subcellular fractionation of rat exorbital lacrimal gland. The distributions of protein and five enzymatic markers define a total of 13 physically and biochemically distinct membrane populations. These include epithelial cell apical membranes, purified 330-fold with respect to the initial homogenate; basal-lateral membranes, purified 80-fold; mitochondria, purified 19-fold; and a major endoplasmic reticulum population, purified 22-fold. Also apparent is a major Golgi population, which is extensively overlapped by other membrane populations; two populations that can be visualized as forming transitions between the endoplasmic reticulum and Golgi membranes; and several populations with unknown subcellular origins. Most of the markers have complex distributions among the isolated membrane populations; this complexity is consistent with current concepts of the synthesis and recycling of membrane constituents and the regulation of cytosolic electrolyte activities.
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000145:classification / Q000201:enzymology / Q000378:metabolism / Q000648:ultrastructure; D002499:Centrifugation, Density Gradient; D007765:Lacrimal Apparatus / Q000648:ultrastructure*; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D008928:Mitochondria / Q000648:ultrastructure; D051381:Rats / Q000033:anatomy & histology*; D011919:Rats, Inbred Strains
chemical_list: D008565:Membrane Proteins