Comparison and evaluation of different methods for alpha-MSH labelling.
We have studied the behaviour of 125I-labelled alpha-MSH under different experimental conditions. Until now, the chloramine T method had been used by most investigators with variable results. We have tested three other labelling techniques based on 125I mild oxidation: (1) an enzymatic method with lactoperoxidase, (2) a sparingly soluble chloramine method (T.D.G.U.) and (3) modified chloramine T procedure, 'the iodine volatilization method'. Labelled hormone obtained after each kind of iodination was assayed for immunoreactivity. In addition, time course degradation was measured by classical RIA incubation procedures. Charcoal-dextran was used to separate bound and free antigen. We have found chloramine T-iodinated alpha-MSH to be significantly more damaged than preparations obtained by other methods and to be less stable when stored at -18 degrees C. No differences were found between the differently labelled 125I-labelled alpha-MSH fresh preparations in binding to surface receptors of human melanoma cell lines in culture.
D000818:Animals; D002417:Cattle; D002700:Chloramines / Q000378:metabolism; D002850:Chromatography, Gel; D006801:Humans; D007106:Immune Sera / Q000494:pharmacology; D007158:Immunologic Techniques; D007457:Iodine Radioisotopes; D007553:Isotope Labeling / Q000379:methods*; D007784:Lactoperoxidase / Q000378:metabolism; D009074:Melanocyte-Stimulating Hormones / Q000378:metabolism*; D008545:Melanoma / Q000175:diagnosis; D011817:Rabbits; D014105:Tosyl Compounds; D014508:Urea / Q000031:analogs & derivatives / Q000378:metabolism; D014835:Volatilization
D002700:Chloramines; D007106:Immune Sera; D007457:Iodine Radioisotopes; D014105:Tosyl Compounds; C016300:chloramine-T; C012385:1,3,4,6-tetrachloro-3 alpha,6 alpha-diphenylglycoluril; D014508:Urea; D009074:Melanocyte-Stimulating Hormones; D007784:Lactoperoxidase