DEVELOPMENT OF RADIOIMMUNOASSAY .1. PREPARATION OF RADIOLABELED TRACERS THEOPHYLLINE

Therapeutic monitoring of theophylline can be accurately performed by radioimmunoassay (RIA). It is radioactive tracer as an essential reage nt for the development of very sensitive RIA. Direct radiolabeling of theophylline with I-125 is very difficult due to the absence of approp riate functional groups. Hence carboxylic acid of theophylline was tag ged to tyrosine methyl ester and then radiolabeled. The derivatives of theophylline, bearing a propionic acid and butyric acid side chains a t seventh and eight position of theophylline, were synthesised and cou pled to tyrosine methyl ester. Theophylline-tyrosine methyl ester conj ugates were labeled with I-125 using chlora mine - T. Radiolabeled the ophylline was purified by solvent extraction followed by thin layer ch romatography, The purified radiolabeled compound were assessed for the ir radiochemical purity, specific activity and immunoreactivity. Stabi lity studies of radiolabeled compounds were performed with different s olvents at different temperatures. Theophylline serum samples analysed using developed and commercial kits showed the correlation coefficien t of 0.961 (n = 9).