Expression of the genes encoding the rat renal insulin-like growth factor-I system.
Insulin-like growth factor-I (IGF-I) modulates renal function, growth, and repair. IGF-I produced in the kidney is one component of the intrarenal IGF-I system comprising the IGF-I receptor (IGF-IR) and six IGF-binding proteins (IGFBP). Because of the physiologic importance of IGF-I and its potential therapeutic properties, the renal sites of mRNA synthesis for IGF-I, IGF-IR, and IGFBP-I through IGFBP-5 were characterized in rat kidney by in situ hybridization. Anatomical heterogeneity was prominent. IGF-I mRNA was present in the thick ascending limb of Henle in the outer medulla, whereas IGF-IR mRNA was diffusely present at low levels throughout the kidney. IGFBP-I mRNA was localized to cells within the distal convoluted tubules as well as the thick ascending limb of Henle. IGFBP-2 mRNA was expressed in glomeruli, medullary ray collecting ducts, pelvic smooth muscle and uroepithelium, and the papilla tip; IGFBP-3 mRNA was localized to the cortical interstitium, whereas IGFBP-4 mRNA was expressed in proximal tubules, medullary ray collecting ducts, and glomeruli. IGFBP-5 was strongly positive throughout the medulla with lesser expression in the distal convoluted tubules and glomeruli. This study highlights the complexity of the intrarenal IGF-I system. The striking heterogeneity of IGFBP gene expression suggests that the various IGFBP may have diverse modulatory effects on the action of IGF-I or discrete effects of their own.
Rabkin
R
R
Department of Medicine, Stanford University, School of Medicine, CA, USA.
Brody
M
M
Lu
L H
LH
Chan
C
C
Shaheen
A M
AM
Gillett
N
N
D000818:Animals; D015870:Gene Expression / Q000502:physiology; D017403:In Situ Hybridization; D018969:Insulin-Like Growth Factor Binding Proteins / Q000235:genetics / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism*; D007668:Kidney / Q000166:cytology / Q000378:metabolism*; D008297:Male; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley
D018969:Insulin-Like Growth Factor Binding Proteins; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I