Growth Hormone Non-dependent Insulin-like Growth Factor-I of Kidney

Han, Sang Won; Choi, Hak Ryong; Choi, Seung Kang

Abstract

Recent studies have revealed that IGF- I produced in kidney are of two fractions; GH dependent and GH nondependent IGF-I. The role of GH nondependent IGF-I is interesting in renal hypertrophy and glomerulosclerosis because GH is clearly related with hypertrophy accompanying glomerulosclerosis is not seen in GH deficient animal. The relationship of the high protein diet and the IGF- I production under the deprivation of GH was studied. In hypophysectomized Sprague-Dawley rat, the level of serum IGF-I was measured using radioimmunoassay, and renal IGF- I production evaluated by immunohistochemistry during both normal and high protein diet. Serum IGF-I of rats on high protein diet was significantly higher than that fed normal protein diet. After unilateral nephrectomy, the level of serum IGF-I was significantly increased in both normal and high protein diet groups. Henle's loop, distal convoluted tubule and collecting duct were weakly stained with normal protein diet. With high protein diet, the staining intensities increased at these portion , and distal part of proximal convoluted tubule and straight tubule were weakly stained. After unilateral nephrectomy, distal convoluted tubule and collecting duct were densely stained with normal protein diet. With high protein diet, the staining intensities increased in distal part of proximal convoluted tubule and Henle's loop. Regardless of the types of protein diet, the specific difference between unilateral nephrectomized rats and sham- operated rats was immunoreactivity of the distal convoluted tubule.. In conclusion, it is suggested that GH non-dependent IGF-I is mainly produced in distal convoluted tubule during compensatory renal hypertrophy, and protein diet mainly affect IGF- I production of distal part of proximal convoluted tubule and Henle's loop.