Cell-specific regulation of mRNAs for IGF-I and IGF-binding proteins-4 and -5 in streptozotocin-diabetic rat kidney

Abstract

Streptozotocin (STZ)-induced diabetes in the rat causes early renal enlargement preceded by a transient elevation in IGF-I content and an increase in IGF-I tissue binding. The effects of IGF-I are mainly mediated through the IGF-I receptor (IGF-IR) and modulated by six specific IGF-binding proteins (IGFBPs). We investigated the gene expression of IGF-I, IGF-IR and IGFBPs at a cellular level within the kidney using in situ hybridisation techniques in short-term (7 day) STZ-diabetic, insulin-treated euglycaemic and normal rats. In diabetes, IGFBP-1 mRNA showed markedly increased expression in distal tubules, collecting ducts and thick ascending limbs of Henle (TALs). IGF-I, and IGFBP-4 and -5 ..