Thyroid hormone and growth hormone interact to regulate insulin-like growth factor-I messenger ribonucleic acid and circulating levels in the rat.

摘要: Thyroid hormones influence growth in part by altering the secretion and effects of GH. GH, turn, mediates its regulating synthesis insulin-like factor-I (IGF-I). IGF-I is a pleiotropic factor that synthesized many tissues acts on to regulate both cellular replication differentiated function. We have studied direct thyroid combined GH regulation hypophysectomized (hypox) rats vivo. All rats, except normal littermates hypox control group, received 100 micrograms hydrocortisone/100 g BW for 10 days. Circulating was measured specific RIA (normal 1 U/ml), hepatic mRNA Northern blot hybridization with an antisense cRNA probe. 1) Hypox treated hGH (75 micrograms, ip, twice daily) days gained 17 vs. 70 littermates. markedly increased circulating (0.52 +/- 0.14 U/ml 12 h after last injection 0.03 0.02 controls). 2) T4 (1 micrograms/100 BW, ip) neither weight, mRNA, nor IGF-I. 3) Rats followed single mg levels comparably as receiving acute alone (IGF-I, h, 0.31 0.09 0.36 0.06 U/ml). 4) T3 (1.5 had slightly but showed no significant change levels. 5) A plus above those injected serum 0.48 0.12 compared alone. 6) After treatment, lowered 0.16 U/ml, 6 T3). These studies demonstrate relatively little effect can major GH-stimulated secretion. The pattern these depends integrity pituitary gland, prior exposure liver and/or hormones, temporal relationship between hormone administration.