Preparation of ¹²⁵I-labelled Synthetic Porcine Secretin for Radioimmunoassay

Abstract

Schaffalitzky de Muckadell, O. B. & Fahrenkrug, J. Preparation of ¹²⁵I-labelled Synthetic Porcine Secretin for Radioimmunoassay. Scand. J. clin. Lab. Invest. 36, 661–668, 1976.

Synthetic porcine secretin was labelled by the conjugation-labelling method of Bolton & Hunter, the lactoperoxidase method, the gaseous diffusion method, and the chloramine-T method. The chloramine-T technique was adapted as routine method. Ten µg (3.27 nmol) peptide was reacted with 5 mCi of Na¹²⁵I at a concentration of chloramine-T of 1.3 mmol/1. Synthetic secretin was suitable for labelling for at least eight months when stored as dry matter in nitrogen-filled glass ampoules. Purification and separation of labelled from unlabelled hormone was carried out by gel-permeation chromatography on Sephadex G-50 superfine. The labelled preparation had a specific radioactivity of 405±33 µCi/nmol (mean ±S.E.M., n=9) and was usable for six weeks. 6-tyrosyl-secretin took up more iodine compared to porcine synthetic secretin but had lower immunoreactivity with all antisera tested.

Key Words:

• Radioimmunoassay
• radioiodination
• secretin
• secretin labelling