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Basic fibroblast growth factor (bFGF) immunoreactivity is present in chromaffin granules
R Westermann1, M Johannsen, K Unsicker
1Department of Anatomy and Cell Biology, University of Marburg, F.R.G.
Insights
Basic fibroblast growth factor (bFGF) is found in bovine adrenal glands, specifically within secretory granules of medullary chromaffin cells. This growth factor exhibits neurotrophic activity, indicating its functional role in neuronal development.
Area of Science:
- Endocrinology
- Neuroscience
- Molecular Biology
Background:
- Basic fibroblast growth factor (bFGF) is a key signaling molecule involved in cell growth and differentiation.
- The presence and function of bFGF in the adrenal gland, particularly in secretory organelles, remain largely uncharacterized.
Purpose of the Study:
- To investigate the localization and forms of bFGF within bovine adrenal glands.
- To assess the neurotrophic activity of bFGF isolated from adrenal tissues.
Main Methods:
- Immunohistochemistry and immuno-electronmicroscopy were used to determine bFGF localization.
- Western blot analysis identified different molecular weight forms of bFGF.
- Neurotrophic activity was assessed using chick ciliary ganglion neurons.
Main Results:
- bFGF was detected in both the adrenal cortex and medulla, with specific localization in secretory granules of medullary chromaffin cells.
- Western blots revealed the typical 18-kDa bFGF and higher molecular weight forms (24, 30, 46 kDa).
- Adrenal bFGF fractions demonstrated significant neurotrophic activity, which was neutralized by antibodies.
Conclusions:
- This study provides the first evidence for bFGF localization within a cellular secretory organelle in the adrenal gland.
- The findings suggest the existence of novel, higher molecular weight immunoreactive forms of bFGF.
- Adrenal bFGF possesses functional neurotrophic properties, highlighting its potential role in neuroendocrine regulation.
Abstract:
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. Immunoreactivity 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 approximately 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.
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