title: Investigation of a possible correlation between rates of secretion and microsomal membrane association of plasma proteins synthesized by rat liver.
abstract: The rates of secretion of complement C3, haptoglobin and plasminogen have been determined after pulse labelling with [3H]leucine, and compared to the secretion of prothrombin, albumin and transferrin investigated previously (Kvalvaag, A.H., Tollersrud, O.K. and Helgeland, L. (1988) Biochim. Biophys. Acta 937, 319-327). To study membrane association, rough microsomes were treated with increasing concentrations of saponin, sodium deoxycholate or Triton X-100. All six proteins were quantitated in the soluble and membrane fraction by enzyme immunoassays. At concentrations of saponin from 0.08% to 0.32%, each secretory protein showed a characteristic distribution, almost identical to that obtained with 0.05% sodium deoxycholate or 0.08% Triton X-100. Albumin and transferrin with half-times for secretion (t1/2) 30 and 75 min, respectively, are both almost exclusively found in the luminal fraction (greater than 95%). Prothrombin and plasminogen, which both show an intermediate t1/2 (approx. 55 min), are partially associated with the membranes, as only about 60% was released. Haptoglobin and complement C3 also show some association with the membranes (80-85% released). C3 is secreted at the same rate as prothrombin and plasminogen (t1/2 = 55 min), whereas haptoglobin is secreted more rapidly (t1/2 = 40 min). Accordingly, no correlation between kinetics of secretion and membrane association was demonstrated.
authors.affiliation: Department of Biochemistry, University of Oslo, Norway.
authors.forename: A H
authors.initials: AH
authors.lastname: Myrset
authors.forename: B R
authors.initials: BR
authors.lastname: Johnsen
authors.forename: M A
authors.initials: MA
authors.lastname: Kulseth
authors.forename: I
authors.initials: I
authors.lastname: Wassdal
authors.forename: L
authors.initials: L
authors.lastname: Helgeland
mesh_terms: D000818:Animals; D001798:Blood Proteins / Q000096:biosynthesis* / Q000378:metabolism; D003176:Complement C3 / Q000096:biosynthesis / Q000378:metabolism; D003902:Detergents; D004797:Enzyme-Linked Immunosorbent Assay; D006242:Haptoglobins / Q000096:biosynthesis / Q000378:metabolism; D007425:Intracellular Membranes / Q000378:metabolism*; D008297:Male; D008862:Microsomes, Liver / Q000378:metabolism*; D010958:Plasminogen / Q000096:biosynthesis / Q000378:metabolism; D011233:Precipitin Tests; D011516:Prothrombin / Q000096:biosynthesis / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012709:Serum Albumin / Q000096:biosynthesis / Q000378:metabolism; D014168:Transferrin / Q000096:biosynthesis / Q000378:metabolism
chemical_list: D001798:Blood Proteins; D003176:Complement C3; D003902:Detergents; D006242:Haptoglobins; D012709:Serum Albumin; D014168:Transferrin; D011516:Prothrombin; D010958:Plasminogen