Increase in muscle IGF-I protein but not IGF-I mRNA after 5 days of endurance training in young rats

Alon Eliakim, Mark Moromisato, David Moromisato, J. O.Anne Brasel, Charles Roberts, Dan M. Cooper

    Research output: Contribution to journalArticle

    67 Scopus citations

    Abstract

    Five days of treadmill training in rats leads to increased muscle size and running time. This was used to examine the effect of exercise on circulating insulin-like growth factor I [IGF-I; radioimmunoassay (RIA)], local muscle (hindlimb) IGF-I (by RIA), and muscle IGF-I mRNA (by ribonuclease protection assay). Eight-week-old female Sprague-Dawley rats were divided into three groups: control (n = 10); single-exercise test (n = 10), untrained but with one maximal exercise test at the and of the study; and training (n = 16), trained for 5 days and one maximal exercise test on day 6. There were no differences among the groups with respect to circulating IGF-I. Muscle IGF-I protein in trained rats (4.2 ± 1.5 ng/g of muscle tissue) was significantly greater than both control (0.27 ± 0.1 ng/g) and single-exercise test (0.62 ± 0.19 ng/g, P < 0.05 by analysis of variance). There was no difference among the groups in IGF-I mRNA gene expression. These data suggest that there is an early, marked, local muscle increase in IGF-I protein in response to exercise. This increase, however, may not be related to increased muscle IGF-I gene expression. Moreover, the IGF-I response was probably local in nature since it was not matched by any increase in circulating IGF-I.

    Original languageEnglish (US)
    Pages (from-to)R1557-R1561
    JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
    Volume273
    Issue number4 42-4
    StatePublished - Nov 17 1997

    Keywords

    • Exercise
    • Gene expression
    • Growth factor

    ASJC Scopus subject areas

    • Physiology
    • Physiology (medical)

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