Early effects of streptozotocin-induced diabetes on insulin-like growth factor-I in the kidneys of growth hormone-transgenic and growth hormone-deficient dwarf mice.

BACKGROUND: The renal growth and hyperfiltration observed in humans and animals with early diabetes might be dependent on growth hormone (GH) and insulin-like growth factor (IGF)-I. The aim of this study was to investigate the early changes in kidney IGF-I in experimental diabetes in mice transgenic for bovine GH and in genetically GH-deficient Ames dwarf mice. METHODS: At 2, 4 and 8 days after a single intraperitoneal injection with streptozotocin, animals were weighted, bled and killed; plasma was analyzed for glucose and IGF-I. IGF-I levels were determined in tissue from snap-frozen kidney and liver. RESULTS: Body weight decreased significantly after the induction of diabetes. Kidney weight increased significantly in GH-transgenic, but not in normal or dwarf mice. Plasma IGF-I was significantly decreased at day 2 in GH-transgenic and normal mice, while liver IGF-I was increased at day 4 in all mice. Kidney IGF-I increased significantly in normal and GH-transgenic mice and was increased more than 3-fold at day 4 in GH-transgenic mice. In dwarf mice, no kidney IGF-I was detectable. CONCLUSION: The diabetes-induced increase in renal IGF-I is dependent on the presence of GH. GH deficiency may protect diabetic animals from early changes in the kidney.