super(14)C radiolabeling of proteins to monitor biodistribution of ingested proteins

• Published in: Analytical biochemistry Vol. 410; no. 1; pp. 57 - 61
• Main Authors: Davis, Laura DR, Spencer, William J, Pham, van Thong, Ward, Tonya L, Blais, David R, Mack, David R, Kaplan, Harvey, Altosaar, Illimar
• Format: Journal Article
• Language: English
• Published: 01-03-2011
• ISSN: 0003-2697
• DOI: 10.1016/j.ab.2010.11.028

The economical preparation of microgram quantities of super(14)C-labeled proteins by in vacuo methylation with methyl iodide is described. The super(14)C radiolabeling was achieved by the covalent attachment of [ super(14)C]methyl groups onto amino and imidazole groups by reaction in vacuo with [ super(14)C]methyl iodide. The method was tested by investigating the biodistribution of super(14)C in rats that were fed super(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 super(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 super(14)C label into the organs of orogastrically fed 10-day-old Sprague-Dawley rats. [ super(14)C]BSA, [ super(14)C]casein, and [ super(14)C]CD14 were individually prepared with specific radioactivities of 34,400, 18,800, and 163,000 disintegrations per minute (dpm)/ mu g, respectively. It was found that the accumulation of super(14)C label in the organs of [ super(14)C]CD14-fed rats, most notably the persistence of super(14)C in the stomach 480 min postgavage, was temporally and spatially distinct from [ super(14)C]BSA and [ super(14)C]casein-fed rats.