Reduced ob mRNA in hypophysectomised rats is not restored by growth hormone (GH), but further suppressed by exogenously administered insulin-like growth factor (IGF) I.
To examine whether GH and IGF-I participate in the regulation of obese (ob) mRNA expression we determined ob mRNA levels in epididydimal fat pads of hypophysectomised (hypox) rats, hypox rats treated with recombinant human (rh) GH or rhIGF-I and normal, weight-matched controls. We found that 1. ob mRNA was markedly suppressed after hypophysectomy (37 +/- 25% of controls), 2. GH infusion had no effect on ob mRNA, but stimulated IGF-I mRNA in fat pads, 3. IGF-I treatment further suppressed ob mRNA (3.5% +/- 0.6% of controls) and 4. serum insulin levels were decreased in all hypox groups (11.2 to 15.9% of controls). In conclusion, exogenous and GH-induced IGF-I differ in their effects on ob mRNA expression and GH is unable to restore ob mRNA towards normal at low insulin levels.
Böni-Schnetzler
M
M
Department of Medicine, University Hospital, Zürich, Switzerland. +CL41usz@usz.unizh.ch
Gosteli-Peter
M A
MA
Moritz
W
W
Froesch
E R
ER
Zapf
J
J
D000273:Adipose Tissue / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D001835:Body Weight; D017931:DNA Primers; D015342:DNA Probes; D013006:Growth Hormone / Q000494:pharmacology*; D006801:Humans; D007016:Hypophysectomy; D007328:Insulin / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000096:biosynthesis / Q000494:pharmacology*; D020738:Leptin; D008297:Male; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D014176:Protein Biosynthesis; D011506:Proteins / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis*; D051381:Rats; D011919:Rats, Inbred Strains; D011994:Recombinant Proteins / Q000494:pharmacology; D012016:Reference Values; D014158:Transcription, Genetic / Q000187:drug effects
D017931:DNA Primers; D015342:DNA Probes; D007328:Insulin; D020738:Leptin; D011506:Proteins; D012333:RNA, Messenger; D011994:Recombinant Proteins; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone