Fine structure of the autotransplanted pituitary in the red eft, Notophthalmus viridescens

Normal and autotransplanted red eft pituitaries were studied by electron microscopy. In the pars distalis of normal and autotransplanted glands four secretory cell types were observed. In the transplant, two of these showed indications of hypersecretory activity. In the pars intermedia one secretory cell type was found and this also appeared hypersecretory after transplantation. Polymorphonucleocytes and an epitheloid type of cell were found to invade the transplants. The observation of hypersecretory activity in transplants presumably freed from hypothalamic control may shed light on hormonal changes in the normal life cycle. Furthermore, secretory granule release from the pars distalis occurs by the same mechanism as seen in mammalian pancreas and pituitary, that is by granule fusion to the cell surface.