The effect of levamisole on glycogen synthase activity in isolated adi
pocytes was studied. The addition of levamisole to these cells resulte
d in an acute concentration-dependent increase ni glycogen synthase ac
tivity. In contrast, epinephrine, dibutyryl cyclic AMP (DcAMP) and cys
teamine decreased glycogen synthase activity. The stimulatory effect o
f levamisole on the activity of the enzyme was not affected by the pre
sence of epinephrine but was diminished when either DcAMP or cysteamin
e was present. The results of this study suggest that levamisole incre
ases adipocyte glycogen synthase activity by a mechanism that can be r
eversed by the elevation of cAMP.