title: Growth hormone and the expression of mRNAs for matrix proteins and oncogenes in bone.
abstract: To examine the effects of growth hormone (GH) on the expression of the mRNAs of bone matrix proteins, three experiments were carried out with 3-month-old female Sprague-Dawley rats. In the first experiment rats were given a single subcutaneous injection of recombinant human GH (8 mg rhGH/kg b. wt.), sacrificed 15 min, 1 h, 2 h, 4 h, 8 h, 16 h and 24 h later, and RNA isolated from cancellous bone from the distal femoral metaphysis. Growth hormone increased the level of type I collagen mRNA by 187, 417, and 509% over the control level at 15 min, 1 h and 2 h, respectively; the mRNA levels declined to 119 and 99% at 4 and 8 h, respectively, and then rose again to 351 and 423% over the control level at 16 and 24 h, respectively. Osteocalcin mRNA transcript increased by 89, 90, 325, 342, 361, and 407% over the control level at 15 min, 1 h, 2 h, 4 h, 8 h and 16 h, respectively, and fell to 66% at 24 h. The level of IGF-I mRNA increased by 45, 83, 120, 140, and 175% over the control level at 2, 4, 8, 16, and 24 h, respectively. In the second experiment, following the administration of rhGH (8 mg/kg b. wt.) bone osteocalcin mRNA increased by 127, 177, 361, and 413% over the control level at 30 min, 1 h, 2 h and 4 h, respectively; IGF-I mRNAs increased by 38, 33, 87, and 437 at 30 min, 1 h, 2 h and 4 h, respectively, but the levels did not become significant until 2 h; c-fos mRNA increased significantly at 30 min, and c-jun and c-myc mRNAs did not increase until 4 h. In the third experiment, animals were given a single injection of rhGH (8 mg/kg b. wt.) and the animals were bled at timed intervals and acid ethanol-extractable serum IGF-I determined. Serum IGF-I increased significantly only at 12 h following rhGH administration. Our data indicate that GH stimulates a rapid increase in the expression of mRNAs for the bone matrix proteins, type I collagen and osteocalcin, by a mechanism that appears to be independent of IGF-I, the early response oncogenes or an increase in osteoblast number.
authors: Department of Physiology, University of Texas Health Science Center at San Antonio, 78284-7756, USA.
authors: M A
authors: MA
authors: Salih
authors: P B
authors: PB
authors: Orhii
authors: C
authors: C
authors: Chen
authors: D N
authors: DN
authors: Kalu
mesh_terms: D000818:Animals; D015152:Blotting, Northern; D001857:Bone Matrix / Q000187:drug effects / Q000378:metabolism*; D003094:Collagen / Q000235:genetics*; D005260:Female; D016762:Genes, fos / Q000235:genetics; D016758:Genes, jun / Q000235:genetics; D016259:Genes, myc / Q000235:genetics; D019382:Human Growth Hormone / Q000008:administration & dosage / Q000494:pharmacology*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000235:genetics; D009857:Oncogenes / Q000235:genetics*; D015675:Osteocalcin / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000494:pharmacology; D013997:Time Factors; D014158:Transcription, Genetic / Q000235:genetics
chemical_list: D012333:RNA, Messenger; D011994:Recombinant Proteins; D015675:Osteocalcin; D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I; D003094:Collagen