The effect of iodination on the biological and immunological activities of the human growth hormone and prolactin

Abstract

The human growth hormone (hGH) and human prolactin (hPRL) were iodinated with 125I using the lactoperoxidase method and purified by gel filtration on a Sephadex G-100 column and by ion exchange chromatography on a diethyl-aminoethyl (DEAE) cellulose column. Aliquots of the peak fraction on the Sephadex G-100 column and each fraction on the DEAE cellulose column were tested by radioimmunoassay (RIA) using 131I-hGH or 131I-hPRL as a tracer and by bioassay using Nb2 rat lymphoma cells. The ratio of the bioassay and RIA estimates of 125I-hGH was 0.89 +/- 0.15 (mean +/- SD) and that of both estimates of 125I-hPRL was 1.14 +/- 0.16. These data suggest that the lactoperoxidase iodination method is sufficient for labeling hGH and hPRL to a high specific activity without altering their biological integrity.