Short-term Strength Training and the Expression of Myostatin and Igf-i Isoforms in Rat Muscle and Tendon: Differential Effects of Specific Contraction Types.
From: Institute of Sports Medicine, Bispebjerg Hospital-Bldg. 8, 1st Floor, 23 Bispebjerg Bakke, DK-2400 Copenhagen NV, Denmark. katjaheinemeier@hotmail.com
Journal of applied physiology (Bethesda, Md. : 1985)
- Publish Date: Feb 2007
- ISSN: 8750-7587
- Volume: 102
- Issue: 2
- Pages: 573-81
- Medium: Print
- Language: English
- Citation (JAMA): Heinemeier K M, Olesen J L, Schjerling P, et al. Short-term Strength Training and the Expression of Myostatin and Igf-i Isoforms in Rat Muscle and Tendon: Differential Effects of Specific Contraction Types.. J. Appl. Physiol. Feb 2007;102:573-81
Abstract
In skeletal muscle, an increased expression of insulin like growth factor-I isoforms IGF-IEa and mechano-growth factor (MGF) combined with downregulation of myostatin is thought to be essential for training-induced hypertrophy. However, the specific effects of different contraction types on regulation of these factors in muscle are still unclear, and in tendon the functions of myostatin, IGF-IEa, and MGF in relation to training are unknown. Female Sprague-Dawley rats were subjected to 4 days of concentric, eccentric, or isometric training (n = 7-9 per group) of the medial gastrocnemius, by stimulation of the sciatic nerve during general anesthesia. mRNA levels for myostatin, IGF-IEa, and MGF in muscle and Achilles’ tendon were measured by real-time RT-PCR. Muscle myostatin mRNA decreased in response to all types of training (2- to 8-fold) (P < 0.05), but the effect of eccentric training was greater than concentric and isometric training (P < 0.05). In tendon, myostatin mRNA was detected, but no changes were seen after exercise. IGF-IEa and MGF increased in muscle (up to 15-fold) and tendon (up to 4-fold) in response to training (P < 0.01). In tendon no difference was seen between training types, but in muscle the effect of eccentric training was greater than concentric training for both IGF-IEa and MGF (P < 0.05), and for IGF-IEa isometric training had greater effect than concentric (P < 0.05). The results indicate a possible role for IGF-IEa and MGF in adaptation of tendon to training, and the combined changes in myostatin and IGF-IEa/MGF expression could explain the important effect of eccentric actions for muscle hypertrophy.
Mesh Headings (Keywords): Animals, Female, Gene Expression Regulation, Hypertrophy, Insulin-Like Growth Factor I, Isometric Contraction, Muscle Contraction, Muscle, Skeletal, Physical Conditioning, Animal, Protein Isoforms, RNA, Messenger, Random Allocation, Rats, Rats, Sprague-Dawley, Tendons, Transforming Growth Factor beta
Check for Full Text / PubMed Unique Identifier (PMID): 17038487
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