Growth hormone (GH) stimulates insulin-like growth factor-I (IGF-I) and IGF-binding protein (IGFBP)-2 gene expression in spleens of juvenile rats.
Growth and development of the spleen involves the growth hormone (GH)/insulin-like growth factor-I (IGF-I) axis. To evaluate the molecular mechanism of these effects we studied the effect of hypophysectomy (Hx) and GH replacement therapy on the expression of IGF-I, the IGF-I receptor and IGF-binding protein-2 (IGFBP-2) in juvenile rats. Hx resulted in a 30% reduction in body weight. GH replacement therapy for seven days partially prevented these effects. IGF-I mRNA levels were reduced 30% by Hx, IGFBP-2 mRNA levels fell 50% whereas IGF-I receptor mRNA levels were unaffected. GH therapy prevented the reduction in IGF-I and IGFBP-2 mRNA levels. These results suggest that the GH effect on splenic growth and development is via local (paracrine) IGF-I expression, in addition to any effect by circulating (endocrine) IGF-I.
Yakar
S
S
Diabetes Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institute of Child and Human Development, National Institutes of Health, Bethesda, Maryland.
Domene
H
H
Meidan
R
R
Cassorla
F
F
Gilad
I
I
Koch
I
I
Laron
Z
Z
Roberts
C T
CT
LeRoith
D
D
Eshet
R
R
D000818:Animals; D002352:Carrier Proteins / Q000235:genetics*; D005786:Gene Expression Regulation / Q000187:drug effects*; D013006:Growth Hormone / Q000097:blood / Q000494:pharmacology*; D018971:Insulin-Like Growth Factor Binding Protein 2; D007334:Insulin-Like Growth Factor I / Q000235:genetics*; D008297:Male; D009929:Organ Size / Q000187:drug effects; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D017526:Receptor, IGF Type 1 / Q000235:genetics; D013154:Spleen / Q000187:drug effects / Q000378:metabolism*
D002352:Carrier Proteins; D018971:Insulin-Like Growth Factor Binding Protein 2; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; D017526:Receptor, IGF Type 1