SHORT COMMUNICATION

Expression of Neuronal Growth Inhibitory Factor (Metallothionein-III) in the Salivary Gland

Y. IRIE^1,2, F. MORI², W. MING KEUNG³, Y. MIZUSHIMA¹, K. WAKABAYASHI<sup>2

1</sup>Department of Geriatrics and Medicine, ²Department of Molecular Biology, Institute of Brain Science, Hirosaki University School of Medicine, Hirosaki, Japan and 3Department of Pathology-CBBSM, Harvard Medical School, Boston, MA, USA

Received September 15, 2003
Accepted December 9, 2003


Summary
Metallothioneins (MTs) are metal-binding proteins that have been regarded as intrinsic factors for protecting cells and tissues from metal toxicity and oxidants. Among the three major classes of MTs, MT-III is different from other MTs because it has neuronal inhibitory activity and is only expressed in the central nervous system. Recent studies, however, have confirmed that MT-III is also expressed in organs other than the brain. These findings not only indicate that MT-III has a much wider tissue distribution than was originally thought, but also suggest that it might have other unknown activities. In the present study, we examined the human salivary and thyroid glands and demonstrated that the MT-III gene is also expressed in the salivary but not in the thyroid gland. While salivary ducts showed intense immuno-reactivity with anti-MT-III, weak immunoreactivity was observed in acinar cells. This, together with the findings that some neuromodulators (i.e. nerve growth factor, etc.) exist in the salivary gland and that MT-III may participate in the transport in renal tubules, suggest that MT-III may have other functions than cytoprotection in the salivary gland.


Key words
Metallothionein-III • MT-III • GIF • Salivary gland • NGF