Preparation of iodine-125-labeled insulin for radioimmunoassay: comparison of lactoperoxidase and chloramine-T iodination.
The enzymatic radioiodination of porcine insulin by a system consisting of lactoperoxidase, hydrogen peroxide, and Na125I was compared with a modified chloramine-T technique. Satisfactory specific activity of the labeled hormone was obtained with the enzymatic iodination, with much greater immunoreactivity and stability than after chloramine-T, besides being quite suitable for the measurement of low plasma insulin levels. There was a positive and highly significant correlation between the insulin concentrations measured with the two tracers, with the regression line defined by the equation: y (chloramine-T) = 8.34 + 0.99 x (lactoperoxidase).
D000818:Animals; D002700:Chloramines; D006801:Humans; D006861:Hydrogen Peroxide; D007202:Indicators and Reagents; D007328:Insulin; D007457:Iodine Radioisotopes; D007553:Isotope Labeling / Q000379:methods*; D007784:Lactoperoxidase; D010544:Peroxidases; D011863:Radioimmunoassay; D013552:Swine
D002700:Chloramines; D007202:Indicators and Reagents; D007328:Insulin; D007457:Iodine Radioisotopes; D006861:Hydrogen Peroxide; D007784:Lactoperoxidase; D010544:Peroxidases