Basic Fibroblast Growth Factor (bFGF) Immunoreactivity Is Present in Chromaffin Granules

: Basic fibroblast growth factor (bFGF) has recently been isolated from bovine adrenal glands. Immunohistological data revealed its presence in both adrenal cortex and adrenal medulla. Using immuno-electronmicroscopy, we found that in medullary chromaffin cells bFGF-immunoreactivity is localized in the secretory granules. Immuno-reactivity also was observed by electronmicroscopy in isolated granules. Western blot analysis revealed the presence of the typical 18-kDa bFGF and additional immunoreactive materials with molecular masses of ∼ 24, 30, and 46 kDa in whole bovine adrenal, and in cortex and medulla. Similar results were obtained with proteins from bovine chromaffin granules, with the following two exceptions: the 46-kDa immunoreactivity was found to be highly enriched when compared with medulla or cortex, and the 18-kDa band could be detected with only an antiserum against a synthetic peptide comprising the 24 NH2-terminal amino acids of bFGF, and not with an antiserum against purified bovine pituitary bFGF. All fractions enriched for bFGF-immunoreactivity showed neurotrophic activity for chick ciliary ganglion neurons, which could be blocked by antibodies. These results demonstrate for the first time the localization and occurrence of bFGF in a cellular secretory organelle, and present further evidence for the existence of higher molecular weight immunoreactive forms of bFGF.