The metabolism of labeled parathyroid hormone. II. Methodological studies.

Further studies on the preparation of 125I-labeled, biologically active parathyroid hormone have resulted in improvements in the procedure, in the storage of the labeled product, and in the establisment of the location of the label in the polypeptide chain. Approximately 95% of the label is on the single tyrosyl residue, amino acid 43, in the bovine hormone. New procedures have also been developed for the isolation and quantitative gel filtration of the labeled hormone deposited in tissues (liver, kidney and bone).