COMPARATIVE-STUDY IN-VIVO AND IN-VITRO OF UNIFORMLY C-14-LABELED AND I-125 LABELED RECOMBINANT FIBROBLAST GROWTH-FACTOR-2

Recombinant bovine fibroblast growth factor (FGF2), uniformly labelled with C-14 ([C-14]FGF2), was purified and showed to be highly stable a nd to retain full biological activity. Orsan distribution of [C-14]FGF 2 after intravenous injection of young rats was assessed by autoradiog raphy of whole body sections and compared with those obtained with [I- 125]iodinated FGF2 (I-125-FGF2). Thyroid, stomach, intestine, bladder and skin were radioactive ly labelled only in the case of I-125-FGF2. This tissue-labelling is artefactual, probably due to free iodide bind ing not observed when using [C-14]FGF2. High-resolution autoradiograph y showed a complex tissue distribution of [C-14]FGF2 in kidney and adr enal organs. Incubation of frozen eye sections with [C-14]FGF2 showed a specific and high-resolution labelling pattern of ocular tissues. Af ter cellular internalization, [C-14]FGF2 was processed into five disti nct polypeptides of 16, 14, 8, 7, and 5.5 kDa. The 14-kDa and 7-kDa po lypeptides are novel catabolic fragments not detected With radioiodina ted FGF,. In terms of stability, tissue distribution specificity, and autoradiographic resolution, [C-14]FGF2 proved to have more advantages than I-125-FGF2 for pharmacokinetic and catabolism studies.