Insulin-like growth factor I in initial renal hypertrophy in potassium-depleted rats.
We investigated insulin-like growth factor I (IGF-I) in the kidney during the initial renal enlargement induced by dietary K depletion in rats. Kidney weight increase was significant after 3 days of K depletion and amounted to 29% after 7 days compared with pair-fed controls [839 +/- 34 vs. 648 +/- 17 mg (SE), P less than 0.01]. The kidney growth occurred despite almost complete arrest in body weight gain in K-depleted animals (8 +/- 3 vs. 34 +/- 4 g/7 days in controls, P less than 0.01). Whole kidney protein, RNA, and DNA estimations indicated that cellular hypertrophy during the first 4 days was followed by hyperplasia. Immunoassayable kidney IGF-I concentration increased by 106% (673 +/- 30 vs. 327 +/- 14 ng/g, P less than 0.01) in K-depleted animals 24 h after induction of K depletion, stayed elevated until day 4, and returned to control levels on day 7. After K depletion for 24 h, IGF-I immunostaining was markedly increased in the medullary parts of the collecting ducts from K-depleted animals, whereas kidney IGF-I gene expression (IGF-I mRNA) had decreased by 36%. The increase in total kidney IGF-I concentration and immunostainable IGF-I in collecting ducts in kidneys from K-depleted rats precedes the renal hypertrophy and thereby suggests a renotropic role for IGF-I. The increase in kidney IGF-I concentration is not associated with increased IGF-I mRNA levels, indicating that non-transcriptional mechanisms may be responsible for the renal IGF-I accumulation.
Flyvbjerg
A
A
Institute of Experimental Clinical Research, University of Aarhus, Denmark.
Marshall
S M
SM
Frystyk
J
J
Rasch
R
R
Bornfeldt
K E
KE
Arnqvist
H
H
Jensen
P K
PK
Pallesen
G
G
Orskov
H
H
D000818:Animals; D004247:DNA / Q000378:metabolism; D004435:Eating; D006984:Hypertrophy; D007150:Immunohistochemistry / Q000379:methods; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism*; D007668:Kidney / Q000378:metabolism / Q000473:pathology*; D008099:Liver / Q000378:metabolism; D008297:Male; D011191:Potassium Deficiency / Q000378:metabolism*; D012313:RNA / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000097:blood; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013194:Staining and Labeling; D015430:Weight Gain
D012333:RNA, Messenger; D012313:RNA; D007334:Insulin-Like Growth Factor I; D004247:DNA; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase