Expression of the insulin-like growth factor system in the hypokalemic rat kidney.
We studied the renal expression of the insulin-like growth factor (IGF) system to gain a better perspective of its potential role in the hyperplastic adaptation of the distal nephron to potassium deficiency. Rats were pair fed 1% or 0.002% potassium diets for periods up to 10 days. IGF-I mRNA was diminished in potassium-deficient rats within 4 days, whereas mRNA for IGF binding protein-1 (IGFBP-1), a collecting duct-associated protein, was increased by day 7. At day 10 mRNA for IGFBP-1 in potassium-deficient animals averaged 2.07 +/- 0.53 (mean +/- SD, relative densitometry units) compared with 0.89 +/- 0.26 in control rats (n = 4, P = 0.002). Conversely, IGFBP-3, a binding protein whose mRNA has been localized to the interstitial compartment, averaged 2.40 +/- 0.02 in potassium-deficient rats and 4.77 +/- 0.05 in controls (n = 4, P < 0.03) at day 10 of treatment. Immunohistochemistry performed using a specific IGFBP-1 antibody revealed hyperplasia of distal nephron segments along with an increase in IGFBP-1 in potassium-depleted rats. These data suggest that IGFBP-1 may play an important role in the control of cellular adaptations in the hypokalemic rat kidney either directly by influencing cell migration or indirectly by localizing IGF-I to the distal nephron.
Rohan
R M
RM
Department of Obstetrics and Gynecology, University of Maryland Medical School, Baltimore 21201, USA.
Unterman
T G
TG
Liu
L
L
Hise
M K
MK
D000818:Animals; D015870:Gene Expression; D007008:Hypokalemia / Q000378:metabolism*; D007150:Immunohistochemistry; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000235:genetics / Q000378:metabolism*; D018971:Insulin-Like Growth Factor Binding Protein 2 / Q000235:genetics / Q000378:metabolism*; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000235:genetics / Q000378:metabolism*; D018974:Insulin-Like Growth Factor Binding Protein 4 / Q000235:genetics / Q000378:metabolism*; D018975:Insulin-Like Growth Factor Binding Protein 5 / Q000235:genetics / Q000378:metabolism*; D018976:Insulin-Like Growth Factor Binding Protein 6 / Q000235:genetics / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism*; D007668:Kidney / Q000378:metabolism*; D008297:Male; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D017526:Receptor, IGF Type 1 / Q000235:genetics*; D013997:Time Factors
D018970:Insulin-Like Growth Factor Binding Protein 1; D018971:Insulin-Like Growth Factor Binding Protein 2; D018972:Insulin-Like Growth Factor Binding Protein 3; D018974:Insulin-Like Growth Factor Binding Protein 4; D018975:Insulin-Like Growth Factor Binding Protein 5; D018976:Insulin-Like Growth Factor Binding Protein 6; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D017526:Receptor, IGF Type 1