mRNA expression of the IGF system in the kidney of the hypersomatotropic rat.
OBJECTIVE
To examine the response of the insulinlike growth factor (IGF) system in the kidney during a state of extreme growth.


METHODS
We studied the mRNA expression of IGF-I, IGF-I receptor, and IGF-binding proteins (BP) using sensitive RNase protection assays following subcutaneous implantation of growth hormone pituitary cells (GH(3)) in rats.


RESULTS
Within 5 weeks, the serum GH levels increased from 18.0 +/- (SE) 5.0 ng/ml in control animals to 389.8 +/- 30.3 ng/ml in GH(3) rats (n = 5, p < 0.001). The circulating IGF-I levels were also elevated. The kidney weights increased from 0.74 +/- 0.01 g in controls to 1.06 +/- 0.03 g in GH(3) animals (n = 5, p < 0.001). Similar changes were observed at week 10. The renal IGF-I mRNA averaged 1.0 +/- (SD) 0.33 relative densitometry units in controls (n = 4) and increased to 2.11 +/- 0.13 relative densitometry units in GH(3) rats (n = 5, p < 0.001). On the other hand, mRNA for the type I IGF receptor decreased in hypersomatotropic rats. Messenger RNAs for IGFBP-1 and IGFBP-4, which have been localized to renal tubules, both decreased significantly following growth induction, while IGFBP-3, the mRNA of which has an interstitial localization, was increased at week 10.


CONCLUSIONS
These data suggest that there is a dynamic relationship between tubular and interstitial compartments with regard to the IGF system in the kidney which may be important in the regulation of the cell mass.
Hise
M K
MK
Division of Nephrology, Department of Medicine, University of Maryland Medical School, Baltimore, MD 21201, USA. mhise@umaryland.edu
Salmanullah
M
M
Tannenbaum
G S
GS
Rohan
R M
RM
D000818:Animals; D001835:Body Weight; D017690:Cell Transplantation; D005260:Female; D013006:Growth Hormone / Q000494:pharmacology / Q000502:physiology*; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism*; D007668:Kidney / Q000378:metabolism*; D009929:Organ Size; D010902:Pituitary Gland; D012333:RNA, Messenger / Q000096:biosynthesis*; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors
D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone