Immunocytochemical localization of thyroglobulin in the transforming endostyle of anadromous sea lampreys, Petromyzon marinus L., during metamorphosis

Light and electron microscopic immunocytochemistry was used to detect the localization of thyroglobulin (TG) in the transforming endostyle of the anadromous sea lampreys, Petromyzon marinus L., during metamorphosis. TG is found within the transforming endostyle throughout metamorphosis (stages 1 to 7) and in early stages (1–2) staining for TG is similar to that observed in the endostyle of the ammocoete. By stage 3, most of the TG is found in large bodies that accumulate within type 3 cells. At stage 4 immunostaining for TG is found within the epithelial cells of the transforming endostyle and in the lumina of some of the first formed follicles. Most of the follicular lumina contain TG by the end of metamorphosis (stage 7). TG in the young parasitic adult lamprey is localized within the follicular lumina, colloid droplets, and occasionally in large bodies found in some of the follicular epithelial cells.