Differentiation of striated muscle fibers in pituitary gland grafts transplanted beneath the kidney capsule.

Striated muscle fibers appear with regularity in pituitary isografts transplanted beneath the kidney capsule. These differentiated striated muscle fibers consist of multinucleated cells resembling skeletal muscle fibers. They appear mainly in the pars distalis, though occasionally in the pars intermedia of the grafts. Although most glandular cells disappeared due to necrosis in the center of the grafted anterior pituitary, where the striated muscle fibers occurred, the folliculo-stellate cells were well preserved in this region and formed elongated myotube-like structures. The muscle fibers appearing in the central pars distalis were in close contact to the folliculo-stellate cells and also to the marginal epithelium of the pituitary cleft. In these cases the striated muscle fibers and folliculo-stellate cells were surrounded by a common basal lamina. This close association between heterotopically differentiated muscle fibers and the normally occurring folliculo-stellate cells strongly suggests a close relationship in differentiation and function between these different cells.