ISOLATION AND PARTIAL MOLECULAR CHARACTERIZATION OF BASIC FIBROBLAST GROWTH-FACTOR FROM ISOLATED PORCINE THYROID-FOLLICLES AND ENTIRE PORCINE THYROID-GLANDS

Immunoreactive basic fibroblast growth factor (bFGF) could be isolated from the cytosol preparation of isolated porcine thyroid follicles as well as in the conditioned medium from thyroid follicles in suspensio n culture. A double band with 16 500 and 15 500 D was detected on sodi um dodecyl sulfate polyacrylamide gel electrophoresis. In dot blot and western blot the isolated peptide was immunoreactive with a specific anti-bovine bFGF antibody. For further biochemical characterization, b FGF was isolated from entire porcine thyroid glands by ammonium sulfat e precipitation, cation exchange chromatography and heparin affinity c hromatography. The material obtained from all three origins was identi cal concerning affinity to heparin and immunoreactivity with the speci fic anti-bovine bFGF antibody and induced neovascularization in the ch orioallantois membranes of chick embryos. Amino acid sequence analysis of the 16-amino-terminal amino acids of the isolated bFGF was in acco rdance with the established complete 146-amino-acid bFGF molecule exce pt that glycine in position 10 is replaced by phenylalanine. An additi onally identified minor peptide presumably is an amino-terminal-trunca ted form of bFGF. missing the first 15 amino acids. We conclude that t he physiological significance of bFGF released by thyroid cells may be the regulation of angiogenesis during thyroid development and goiter growth.