[Growth factors: a regulator of renal function]

We selectively focus on two growth factors, epidermal growth factor (EGF) and insulin-like growth factor (IGF), and discuss their roles on regulation of renal function and associated diseases conditions, as well. EGF, 6 kD polypeptide, is derived by proteolysis from a large precursor (prepro EGF, 133 kD). Prepro EGF is a membrane-anchored protein and its mRNA is predominantly localized to distal tubules of mouse and rat kidneys. We immunohistochemically demonstrated the glomerular distribution of EGF and EGF-receptor in normal and nephritic human kidneys. The physiologic roles of EGF produced in the kidney are various; it is mitogenic for tubular epithelial cell, inhibits gluconeogenesis and salt and water reabsorption in the tubules, and effects on glomerular hemodynamics. Alteration of renal EGF expression is suggested in renal ischemic injury, renal hypertrophy and cystic renal disease. IGF-I, somatomedin-C, is produced in collecting duct, and glomerular cells, and exerts a variety of actions on kidney. IGF-I stimulates gluconeogenesis in renal tubules, and is mitogenic for mesangial cells. The administration of this growth factor increases glomerular filtration rate. Enhanced expression of renal IGF-I was observed in the uninephrectomized animals.