THE EFFECT OF GLUCOCORTICOIDS ON THE ACCUMULATION OF UTROPHIN BY CULTURED NORMAL AND DYSTROPHIC HUMAN SKELETAL-MUSCLE SATELLITE CELLS

Human muscle cultures undergo a long-term loss of myotubes and a decli ne in dystrophin content, which can be prevented by glucocorticoid tre atment of the cultures. We confirmed these findings and extended them to show that the utrophin content of control and dexamethasone-treated normal myotube cultures is not significantly different. In contrast t o normal cultures, the utrophin content of long-term dexamethasone-tre ated DMD myotube cultures was significantly greater than that of the c orresponding untreated cultures. Utrophin mRNA transcript levels norma lized to total poly (A) were unaffected by dexamethasone treatment of either normal or DMD myotube cultures, suggesting the effect of dexame thasone on utrophin accumulation by DMD cultures is mediated post-tran scriptionally. A combination of an increase in myotube numbers and lac k of competition with dystrophin for membrane-binding sites in DMD myo tubes may explain the distinct effects of dexamethasone on utrophin le vels in normal and DMD cultures.