title: Subcellular structure of bovine thyroid gland. VII. A study on the distribution of bovine thyroid plasma membranes by density gradient centrifugation in zonal rotors.
abstract: In order to obtain plasma membrane-rich fractions two methods were tried. Approach A was based on differential pelleting followed by discontinous gradient centrifugation in a B-XIV zonal rotor. In approach B homogeneization was performed in buffered water (NaHCO3, pH 7.4). The 73 300 X g pellet from this homogenate was subjected to buoyant density equilibrium in a HS zonal rotor (continuous sucrose gradient). Using approach A, the highest relative specific activity for plasma membrane markers was found at the 30-37% sucrose interphase. However, an increase for glucose 6-phosphatase (endoplasmic reticulum marker) was also found at that interphase. Using approach B marker profiles different from approach A were found. Approach B results in a subdivision of membrane material in four distinct regions. These regions do not contain completely pure membrane species, although region I seems to be essentially derived from plasma membranes. It is also concluded from approach A that plasma membranes from bovine thyroid tissue are heterogeneous.
mesh_terms: D000818:Animals; D002417:Cattle; D002458:Cell Fractionation / Q000379:methods; D002462:Cell Membrane / Q000648:ultrastructure*; D002501:Centrifugation, Zonal; D013347:Subcellular Fractions / Q000648:ultrastructure; D013961:Thyroid Gland / Q000648:ultrastructure*