Expression of insulin signaling transmitters and glucose transporters at the protein level in the rat testis.

Insulin receptor substrate (IRS) proteins are key mediators in insulin signaling from the insulin receptor. It takes place through receptor-mediated tyrosine phosphorylation of IRS proteins. The aim of the present article is to demonstrate the distribution of IRS 1-3, glucose transporters 1-4 (GLUT 1-4), signal regulatory protein 1alpha (SIRP1alpha), PKB, and PI 3-kinase in the rat testis to see if signal transduction mediated by these proteins is active in testicular cells. Wistar rats were used as donors of testis tissue. Expression of these genes was studied at the protein level by using immunohistochemistry and Western blotting. IRS-1, IRS-2, GLUT 1, GLUT 2, GLUT 3, and SIRP1alpha were strongly expressed in the Sertoli cells (except GLUT 1), early spermatocytes, peritubular myoid cells, macrophage-like interstitial cells, and testicular endothelial cells in all the testes investigated by immunohistochemistry. IRS-2 was also expressed in the Leydig cells. Immunoblotting experiments demonstrated the presence of about 26-67 kDa reactive with anti- IRS-1, IRS-2, GLUT 1, GLUT 2, GLUT 3, PKB, and SIRP1alpha. The present results suggest that proteins like insulin and certain cytokines using IRS-1, IRS-2, GLUT 1, GLUT 2, GLUT 3, PKB, and SIRP1alpha in their signal transduction can have effects on the different types of testicular cells in the rat.