GENE-EXPRESSION OF THE INSULIN-LIKE-GROWTH-FACTOR SYSTEM DURING MOUSEKIDNEY DEVELOPMENT

Expression of the insulin-like growth factor (IGF) system was investig ated in mouse renal development and physiology, using non radioactive in situ hybridization and quantitative RT-PCR. IGF-I mRNA levels incre ased after birth and were confined to distal tubules and peritubular c apillaries in the outer medulla. IGF-II mRNA levels were high in devel oping kidneys and peaked after birth. The type I receptor mRNA express ion pattern mostly parallelled those of IGF-I and IGF-II. The IGF bind ing proteins (IGFBP's) showed weak mRNA expression for IGFBP-1 and -6. High fetal mRNA levels were measured for IGFBP-2, showing a similar p rofile in time as observed for IGF-II. Low fetal IGFBP-3 and -5 mRNA l evels increased after birth. IGFBP-2, -4 and -5 mRNA expression was lo calized to differentiating cells. In the mature kidney predominant exp ression was confined to proximal tubules (IGFBP-4), thin limbs of Henl e's Loop (IGFBP-2), glomerular mesangial cells (IGFBP-5) and peritubul ar capillaries of the medulla (IGFBP-5). IGFBP-3 mRNA was exclusively expressed in endothelial cells of the renal capillary system. Distinct mRNA expression for each member of the IGF system may point to specif ic roles in development and physiology of the mouse kidney. (C) 1997 E lsevier Science Ireland Ltd.