REDUCED OB MESSENGER-RNA IN HYPOPHYSECTOMIZED RATS IS NOT RESTORED BYGROWTH-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 oh mRNA levels in epididydimal fat pads of hypophysectomised (hyper) rats, hyper rats treated with recom binant human (rh) GH or rhIGF-I and normal, weight-matched controls. W e 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 suppress ed ob mRNA (3.5% +/- 0.6% of controls) and 4. serum insulin levels wer e decreased in all hyper groups (11.2 to 15.9% of controls). In conclu sion, exogenous and GH-induced IGF-I differ in their effects on ob mRN A expression and GH is unable to restore ob mRNA towards normal at low insulin levels. (C) 1996 Academic Press, Inc.