Abstract
Changes in skeletal muscle activity cause dramatic alterations in muscle mass. Increased load on a muscle (synergistic overload) results in muscle hypertrophy. During hypertrophy, skeletal muscle concentrations of insulin-like growth factors (IGF-I and IGF-II) mRNAs increase. To clarify the role of IGFs in regulating muscle mass, this study examined whether IGF-I and -II mRNA levels were altered during decreased muscle activity (denervation). Gastrocne-mius weights decreased 4.2%, 7.7%, 18.1%, 27.7%, 35.1%, 45.0%, and 60.3% at 2, 3, 5, 7, 10, 12, and 17 d following denervation, respectively. Muscle DNA content remained constant throughout the first 12 d after surgery, but increased above control levels at day 17. During the first week after surgery, gastrocnemius IGF-II mRNA remained constant. However, IGF-II mRNA abundance was 2.5-fold greater than controls by 10 d of denervation, 3-fold by 12 d, and 6.8-fold by 17 d. On the other hand, IGF-I mRNA levels were not affected by denervation. In conclusion, although increased muscle activity results in a change of IGF-I mRNA expression, decreased muscle activity has no effect on IGF-I mRNA expression. In contrast, IGF-II mRNA levels increase with long-term denervation as well as with increased muscle activity. This study suggests that muscle activity may not be the only factor affecting IGF-I and -II expression.
Original language | English (US) |
---|---|
Pages (from-to) | 1005-1008 |
Number of pages | 4 |
Journal | Medicine and Science in Sports and Exercise |
Volume | 25 |
Issue number | 9 |
DOIs | |
State | Published - Sep 1993 |
Keywords
- Dna
- Female rats
- Gastrocnemius
- Igf
ASJC Scopus subject areas
- Orthopedics and Sports Medicine
- Physical Therapy, Sports Therapy and Rehabilitation