title: (14)C radiolabeling of proteins to monitor biodistribution of ingested proteins.
abstract: The economical preparation of microgram quantities of (14)C-labeled proteins by in vacuo methylation with methyl iodide is described. The (14)C radiolabeling was achieved by the covalent attachment of [(14)C]methyl groups onto amino and imidazole groups by reaction in vacuo with [(14)C]methyl iodide. The method was tested by investigating the biodistribution of (14)C in rats that were fed (14)C-labeled human soluble cluster of differentiation 14 (CD14) protein, a receptor for bacterial lipopolysaccharide. Two other control proteins, bovine serum albumin (BSA) and casein, were also labeled with (14)C and used for comparative analysis to determine the following: (i) the efficacy and cost efficiency of the in vacuo radiolabeling procedure and (ii) the extent of incorporation of the (14)C label into the organs of orogastrically fed 10-day-old Sprague-Dawley rats. [(14)C]BSA, [(14)C]casein, and [(14)C]CD14 were individually prepared with specific radioactivities of 34,400, 18,800, and 163,000 disintegrations per minute (dpm)/microg, respectively. It was found that the accumulation of (14)C label in the organs of [(14)C]CD14-fed rats, most notably the persistence of (14)C in the stomach 480 min postgavage, was temporally and spatially distinct from [(14)C]BSA and [(14)C]casein-fed rats.
authors.affiliation: Department of Biochemistry, Microbiology, and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario, Canada K1H 8M5.
authors.forename: Laura D R
authors.initials: LD
authors.lastname: Davis
authors.forename: William J
authors.initials: WJ
authors.lastname: Spencer
authors.forename: Van Thong
authors.initials: VT
authors.lastname: Pham
authors.forename: Tonya L
authors.initials: TL
authors.lastname: Ward
authors.forename: David R
authors.initials: DR
authors.lastname: Blais
authors.forename: David R
authors.initials: DR
authors.lastname: Mack
authors.forename: Harvey
authors.initials: H
authors.lastname: Kaplan
authors.forename: Illimar
authors.initials: I
authors.lastname: Altosaar
mesh_terms: D000818:Animals; D002250:Carbon Radioisotopes / Q000032:analysis / Q000737:chemistry; D002417:Cattle; D004435:Eating; D005612:Freeze Drying; D006801:Humans; D007553:Isotope Labeling / Q000379:methods*; D008745:Methylation; D011506:Proteins / Q000737:chemistry* / Q000493:pharmacokinetics*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012995:Solubility
chemical_list: D002250:Carbon Radioisotopes; D011506:Proteins