AJP - Endocrinology and Metabolism, Vol 269, Issue 2 E277-E282, Copyright © 1995 by American Physiological Society
Biological activity of immunoreactive insulin-like activity extracted from rat submandibular gland
M. Taouis, D. Deville de Periere, D. Hillaire-Buys, M. Derouet, R. Gross, J. Simon and G. Ribes
Institut National de la Recherche Agronomique, Station de Recherches Avicoles, Endocrinologie de la Croissance et du Metabolisme, Nouzilly, France.
Earlier studies indicate the presence of an insulin-like immunoreactivity
(ILI) in rat submandibular salivary glands (SSG). Previous observations
also showed that streptozotocin (STZ)-induced diabetes was accompanied by
an increase in SSG ILI concentrations. In the present work we studied the
effect of SSG ILI from normal and STZ diabetic rats (ILI-N and ILI-D,
respectively) on insulin receptor binding and function in LMH cell line.
ILI-N and ILI-D inhibited 125I-insulin binding to intact cells and wheat
germ agglutinin (WGA)-purified insulin receptors with a high affinity.
Furthermore, ILI-N and ILI-D activated, although weakly, the beta-subunit
autophosphorylation of solubilized and WGA-purified insulin receptors. An
ATP hydrolytic activity was present in ILI-N and, to a greater extent, in
ILI-D extracts, which can at least in part explain their low potency for
activating autophosphorylation and kinase activity of insulin receptors in
vitro. However, after ILI treatment of intact cells and immunoprecipitation
of insulin receptors, ILI induced a dose-dependent tyrosine phosphorylation
of the insulin receptor beta-subunit. Finally, ILI-N and ILI-D stimulated
amino acid uptake and lipogenesis in LMH cells. These findings suggest that
SSG ILI is biologically active and can participate in metabolic
regulations.
