Effect of training and growth hormone suppression on insulin-like growth factor I mRNA in young rats

J Appl Physiol (1985). 1994 May;76(5):2204-9. doi: 10.1152/jappl.1994.76.5.2204.


The growth hormone (GH)-insulin-like growth factor I (IGF-I) axis plays a role in the adaptation to exercise training, but IGF-I gene expression in response to exercise training and GH suppression has not been studied. Twenty female rates underwent a 4-wk treadmill training program begun in the prepubertal period (day 14 of life). In 10 of the training rats, GH production was suppressed by anti-GH-releasing hormone antibodies (GH suppressed). IGF-I mRNA and protein levels were measured in liver and hindlimb skeletal muscle. GH suppression reduced IGF-I mRNA expression in the liver to a much greater extent than in the muscle. In the GH control rats, training induced significant increases in hepatic exon 1-derived IGF-I mRNA (mean increase 30%; P < 0.05) and muscle exon 2-derived mRNA (mean increase 35%; P < 0.05). In the GH-suppressed rats, only muscle exon 1-derived transcripts were significantly increased by training (55%; P < 0.05) and this was associated with a significant increase in muscle IGF-I protein levels (P < 0.05). We speculate that the anabolic response to training may involve both GH-dependent increases in IGF-I mRNA in the liver and GH-independent increases in the muscle.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Actins / metabolism
  • Animals
  • Autoradiography
  • Female
  • Gene Expression
  • Growth Hormone / antagonists & inhibitors*
  • Insulin-Like Growth Factor I / biosynthesis*
  • Liver / metabolism
  • Muscle Proteins / metabolism
  • Muscles / metabolism
  • Nucleic Acid Hybridization
  • Physical Conditioning, Animal*
  • RNA, Messenger / biosynthesis*
  • Rats
  • Rats, Sprague-Dawley
  • Ribonucleases / metabolism


  • Actins
  • Muscle Proteins
  • RNA, Messenger
  • Insulin-Like Growth Factor I
  • Growth Hormone
  • Ribonucleases