No effect of aging on skeletal msucle insulin-like growth factor mRNAs

Aging muscles do not exhibit a decline in the concentration of precursors to insulin-like growth factors so that these factors cannot account for the muscle atrophy that occurs with aging. The concentration of mRNA for insulin-like growth factors did increase between youth and middle age, but subsequent declines in the growth factors were not seen as the rats progressed from 12 to 24 months of age.