A synergistic effect of glucocorticoids and insulin on the differentiation of myoblasts.

Glucocorticoids and insulin were found to act synergistically to promote differentiation in some clones of the L6 rat myoblast cell line. Other hormone effects on these cells were investigated to determine the extent of the synergism. The insulin stimulation of sugar transport was unaffected by glucocorticoids although they did by themselves slightly enhance transport. Glucocorticoids were found to increase the adhesiveness of the cells--an effect not influenced by insulin. Cyclic AMP levels were found to peak just prior to the time of the onset of fusion and insulin broadened this peak, while the combination of both hormones further lengthened the time for which cyclic AMP levels remained elevated.