title: Partial characterization of low density lipoprotein preparations isolated from fresh and frozen plasma after radiolabeling by seven different methods.
abstract: Four 99mTc and three 123I labeling methods were evaluated for their suitability to label low density lipoproteins (LDL) for the purpose of scintigraphic biodistribution studies. For 99mTc these methods were: direct incorporation in LDL of 99mTcO4- using sodium dithionite (dithionite method); a method using first N,N-dimethylformamide to prepare a 99mTc-complex reacting with LDL in a subsequent step (DMF method); a technique in which 99mTcO4- is first coupled to a diamide dithiolate derivative of pentanoic acid by reduction with dithionite, followed by coupling of this ligand to LDL (N2S2 method); and a method using sodium borohydride and stannous chloride as reducing agents (borohydride method). The iodination techniques were based on oxidation of I(-)----I+, using iodine monochloride (ICl method), 1,3,4,6-tetrachloro-3,6-diphenylglycoluril (Iodogen method), and N-bromosuccinimide (NBS method) as oxidants. We studied labeling yields, modification of LDL caused by the labeling procedures using agarose-gel electrophoresis, and radiochemical stability of the labeled LDL complex upon incubation in plasma at 37 degrees C for 15 h. We used Sepharose CL6B chromatography to separate LDL from other plasma proteins. We also examined whether LDL isolated from frozen plasma (Pool-LDL) gave results similar to LDL obtained from freshly prepared plasma (Fresh-LDL). Pool-LDL radiolabeled by the dithionite, DMF, NBS, and Iodogen methods lost its label upon incubation with plasma. This also happened with Fresh-LDL when the DMF, NBS and Iodogen methods were used. Upon agarose-gel electrophoresis, no modification of LDL was observed with all methods when the radionuclide/LDL ratio was kept low.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Gaubius Institute TNO, Leiden, The Netherlands.
authors.forename: D E
authors.initials: DE
authors.lastname: Atsma
authors.forename: H J
authors.initials: HJ
authors.lastname: Kempen
authors.forename: W
authors.initials: W
authors.lastname: Nieuwenhuizen
authors.forename: F M
authors.initials: FM
authors.lastname: van 't Hooft
authors.forename: E K
authors.initials: EK
authors.lastname: Pauwels
mesh_terms: D000818:Animals; D002850:Chromatography, Gel; D004587:Electrophoresis, Agar Gel; D005069:Evaluation Studies as Topic; D006801:Humans; D007457:Iodine Radioisotopes; D007553:Isotope Labeling / Q000379:methods*; D008077:Lipoproteins, LDL / Q000097:blood* / Q000737:chemistry; D008297:Male; D011817:Rabbits; D013667:Technetium
chemical_list: D007457:Iodine Radioisotopes; D008077:Lipoproteins, LDL; D013667:Technetium