COMPARISON OF IODINE MONOCHLORIDE AND MODIFIED CHLORAMINE-T RADIOIODINATION FOR INVIVO PROTEIN STUDIES

  • 1 January 1977
    • journal article
    • research article
    • Vol. 89  (4) , 836-844
Abstract
Aggregate formation on gel chromatography and shortened in vivo t1/2 [half-time] result from the usual chloramine-T (CT) radioiodination of proteins. A modified CT method with decreased CT:protein ratio has been advocated, particularly for use in the 125I-fibrinogen uptake test. Such modified CT procedures with 131I were assessed by simultaneous injection in rabbits of 125I-monochloride protein standards along with the 131I-CT proteins. Standard clearance analyses were performed. For both albumin and fibrinogen a much reduced CT:protein ratio was required before satisfactory in vivo proteins were obtained. The ratio differed for the 2 proteins, with fibrinogen more susceptible to CT-induced aggregate formation. Intermediate CT:protein ratios resulted in denaturation of only a portion of the labeled proteins as manifested by a low C1 with a normal t1/2 for the slow component. At intermediate ratios, unaggregated protein displayed abnormal clearance kinetics, indicating that denaturation was not solely the result of aggregtates. A modified CT radioiodination may be used for in vivo studies, but only if carefully compared in vivo with more generally used radiolabeling procedures.