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

• Published in: Journal of applied physiology (1985) Vol. 76; no. 5; p. 2204
• Main Authors: Zanconato, S, Moromisato, D Y, Moromisato, M Y, Woods, J, Brasel, J A, Leroith, D, Roberts, Jr, C T, Cooper, D M
• Format: Journal Article
• Language: English
• Published: United States 01.05.1994
• Subjects: 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; Rats; Rats, Sprague-Dawley; Ribonucleases - metabolism; RNA, Messenger - biosynthesis
• ISSN: 8750-7587
• 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.