Characterization of the insulin-signaling pathway in lacrimal and salivary glands of rats.
OBJECTIVE
Insulin has been acknowledged as a mediator of several physiological events in lacrimal and salivary glands. We investigated the presence of insulin receptors and of insulin-induced autophosphorylation of the insulin receptor and activation of elements involved in the early steps of insulin signaling in lacrimal and salivary glands of rats.


METHODS
Lacrimal and salivary glands of Wistar rats were removed and processed for immunohistochemistry using anti-insulin receptor and anti-IGF-1 receptor antibodies. The activation of insulin receptors following insulin treatment, and the involvement of insulin receptor substrates-1 and -2, Shc, JAK-2 and STAT-1, were analyzed by immunoprecipitation, followed by SDS-PAGE and immunoblotting of rat lacrimal and salivary glands after exposure to insulin.


RESULTS
Insulin and IGF-1 receptors were present in rat lacrimal and salivary glands and were located predominantly in the cytoplasm and plasma membrane. Functional studies demonstrated that insulin induced a dose-dependent phosphorylation of the insulin receptor, IGF-1R, insulin receptor substrates-1 and -2, Shc, and STAT-1. In rats with streptozotocin-induced diabetes mellitus there was a significant reduction in insulin-induced insulin receptor and STAT-1 phosphorylation in the lacrimal gland but not in the salivary gland; there was no influence on Shc phosphorylation in either tissue.


CONCLUSIONS
The present results indicate that insulin and IGF-1 receptors are expressed in lacrimal and salivary glands, and that insulin can induce the phosphorylation of its receptor and activate elements involved in the early steps of insulin signaling in both tissues.
Laboratory of Clinical Pathophysiology, Department of Clinical Medicine, School of Medicine, State University of Campinas (UNICAMP), Campinas, SP, Brazil. emrocha@unicamp.br
E M
EM
Rocha
M H
MH
de M  Lima
C R
CR
Carvalho
M J
MJ
Saad
L A
LA
Velloso
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D000818:Animals; D004268:DNA-Binding Proteins / Q000378:metabolism; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D015151:Immunoblotting; D007328:Insulin / Q000494:pharmacology / Q000502:physiology*; D055504:Insulin Receptor Substrate Proteins; D047908:Intracellular Signaling Peptides and Proteins; D053614:Janus Kinase 2; D007765:Lacrimal Apparatus / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011233:Precipitin Tests; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D011518:Proto-Oncogene Proteins; D051381:Rats; D017208:Rats, Wistar; D017526:Receptor, IGF Type 1 / Q000378:metabolism*; D011972:Receptor, Insulin / Q000378:metabolism*; D050794:STAT1 Transcription Factor; D012469:Salivary Glands / Q000187:drug effects / Q000378:metabolism*; D055765:Shc Signaling Adaptor Proteins; D015398:Signal Transduction; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D015534:Trans-Activators / Q000378:metabolism; D014443:Tyrosine / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D033942:Adaptor Proteins, Vesicular Transport; D004268:DNA-Binding Proteins; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; D047908:Intracellular Signaling Peptides and Proteins; C526296:Irs1 protein, rat; C526299:Irs2 protein, rat; D010750:Phosphoproteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; D050794:STAT1 Transcription Factor; D055765:Shc Signaling Adaptor Proteins; C528035:Shc1 protein, rat; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; C494081:Stat1 protein, rat; D015534:Trans-Activators; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D017526:Receptor, IGF Type 1; D011972:Receptor, Insulin; C507927:Jak2 protein, rat; D053614:Janus Kinase 2