Salivary insulin-like growth factor-I originates from local synthesis

Abstract

Insulin-like growth factor-I (IGF-I) is a GH-dependent growth factor found in its highest concentrations in plasma. It is also measurable in saliva. The origins of salivary IGF-I concentrations were studied. Intracardial administration of Sprague-Dawley rats with 125I-labelled IGF-I and subsequent analysis of plasma and saliva samples by exclusion gel chromatography and SDS-PAGE, followed by autoradiography, demonstrated the apparent inability of IGF-I to cross from the plasma pool through to saliva. 125I-Labelled IGF-I was not chromatographed immediately before injection, resulting in administration of free iodide along with the iodinated peptide. This free iodide was demonstrable in saliva, indicating that movement of substances from plasma to saliva was measurable using the levels of 125I activity administered. Free iodide in saliva was not contributed to by 125I-labelled IGF-I degradation since 125I-labelled IGF-I was shown to be stable in saliva over 24 h. These data indicated that IGF-I in saliva is produced locally. Identification of a 4.7 kb IGF-I mRNA transcript in rat parotid salivary gland was consistent with IGF-I synthesis within that tissue.

Salivary gland is capable of GH synthesis under GHRH stimulation

“…Animals treated with placebo were negative for GH mRNA in the two systems used, although low GH-like contents were detected by RIA. Since salivary glands are known to produce at least some peptide hormones (Hauser-Kronberger et al 1992) and especially growth factors (Thesleff et al 1988, Ryan et al 1992, Amano et al 1993, the possibility of a persisting genomic situation allowing GH synthesis cannot be ruled out, although the absence of GH mRNA by PCR-Southern blot and in situ hybridization in the placebo-treated animals does not support this theory. However, the high local content of growth factors, and especially epidermal growth factor from the submaxillary gland could at least play an important role in the GHRH-induced GH synthesis (Ikeda et al 1984).…”

Effects of acute exercise on salivary free insulin-like growth factor 1 and interleukin 10 in sportsmen

“…It has also been reported to be produced locally from the salivary glands with the free forms measurable in saliva. 11,15 Generally, Insulin-like growth factors (IGFs) are peptide hormones that play a pivotal role in growth, and cell division. Hence salivary IGF-1 may be implicated in the regeneration of oral tissues and wound healing.…”

Multifunctional roles of growth factors or biologically active peptides in salivary glands and saliva

“…IGF-I mRNAs in matured rats have been found to be expressed at a higher level in the SMG than in the liver, where they were localized in GCT cells, and a 1.8 kb mRNA for IGF-I was expressed at a lower level in acinar and ductal cells (67). IGF-I in the rat saliva was shown to be produced locally by demonstrating a 4.7 kb IGF-I mRNA transcript in the rat parotid gland, although the highest concentration of IGF-I was found in plasma (68). The parotid gland, devoid of GCT segments, is the main source of IGF-I production, which may take place in its acinar cells, although at a low level.…”