IGF, type I IGF receptor and IGF-binding protein mRNA expression in kidney and liver of potassium-depleted and normal rats infused with IGF-I

• Published in: Journal of molecular endocrinology Vol. 19; no. 1; pp. 59 - 66
• Main Authors: van Neck, J W, Flyvbjerg, A, Schuller, A G, Rosato, R R, Groffen, C, van Kleffens, M, Lindenbergh-Kortleve, D, Dørup, I, Drop, S L
• Format: Journal Article
• Language: English
• Published: England BioScientifica 01.08.1997
• Subjects: Animals; Blood Glucose - analysis; Female; Gene Expression; Insulin-Like Growth Factor Binding Proteins - genetics; Insulin-Like Growth Factor I - administration & dosage; Insulin-Like Growth Factor I - genetics; Insulin-Like Growth Factor I - metabolism; Kidney - metabolism; Kidney - pathology; Liver - metabolism; Liver - pathology; Organ Size; Potassium Deficiency - blood; Potassium Deficiency - genetics; Rats; Rats, Wistar; Receptor, IGF Type 1 - genetics; RNA, Messenger - genetics; Tibia - anatomy & histology; Weight Gain
• ISSN: 0952-5041; 1479-6813
• DOI: 10.1677/jme.0.0190059

ABSTRACT Dietary potassium (K) depletion is known to reduce body weight gain and organ growth, except for kidney which increases in weight. This renal hypertrophy is preceded by increased renal IGF-I levels. In the present study, we investigated IGF-I and -II, type I IGF receptor and IGF-binding protein (IGFBP) mRNA expression in liver and kidney of K-depleted and normal rats infused with vehicle or recombinant human IGF-I. Body weight gain was almost completely arrested in K-depleted rats without any stimulatory effect of IGF-I infusion. Both absolute and relative kidney weight (kidney weight/body weight) were significantly increased in K-depleted rats and this was further enhanced by IGF-I infusion. In contrast, relative liver weight was comparable in the different groups and unaffected by IGF-I infusion. IGF-I mRNA expression was significantly lower in kidney and liver of K-depleted animals whereas type I IGF receptor levels were unchanged. In contrast, in kidney, K depletion increased IGFBP-1 and -2 mRNA expression with no additional effect of IGF-I infusion. In liver of K-depleted animals, IGFBP-1 mRNA expression was increased whereas increased IGFBP-1 and -2 mRNA expression was observed when these animals were infused with IGF-I. These observations may point towards a differential mode of action of the IGFBPs. In kidney increased IGFBP-1 and -2 mRNA expression may enhance IGF-I bioavailability with subsequent kidney growth. In liver, with clearly detectable type I IGF receptor mRNA expression, increased IGFBP levels may protect from IGF-I-induced organ growth by decreasing IGF-I bioavailability.