[Ultrastructure of gonadotropic cells of the normal eel and after estradiol injection].

Male and female silver eels, in fresh water or sea water, have few gonadotrophs (GTH) poorly differentiated. An oestradiol (E2) treatment induces their development: a well developed Golgi area, abundant secretory granules (200-500 nm), dilated cisterna and large globules 1.2-2.2 micron) are observed. A positive feedback may control gonadotropin synthesis in immature eels. No macroscopic effect is discernible on the gonad.