We previously demonstrated the preventive effect of insulin-like growth fac
tor 1 (IGF-1) on steroid myopathy in rats. However, the mechanism by which
IGF-1 inhibits steroid myopathy remains unclear. Recent studies have reveal
ed that glutamine synthetase (GS) is induced by glucocorticoid and may be r
elated to the development of steroid myopathy. In this study, we examined w
hether IGF-1 affected steroid-induced enhancement of GS activity in L6 rat
skeletal muscle cells. Dexamethasone(10(-6) M) significantly increased GS a
ctivity in L6 cells(P < 0.01), IGF-1 dose-dependently inhibited dexamethaso
ne-induced GS activity. Addition of IGF-1 (750 ng/ml) decreased GS activity
to approximately 50% of that with dexamethasone alone (P < 0.01). These re
sults suggest that a decrease in GS activity may be involved in the prevent
ive effect of IGF-1 on steroid myopathy. (C) 2001 Elsevier Science Ireland
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