Immunohisto- and immunocytochemical studies on the dynamics of TSH and GTH cells in normally metamorphosing, metamorphosed, and metamorphosis-arrested Hynobius retardatus.

The development and dynamics of TSH and GTH cells were studied immunohisto- and immunocytochemically in the salamander Hynobius retardatus, which had been reported to show neoteny in a specific environment and a precocious development and maturation of testis in goitrogen-treated larvae. Pituitary glands from normally metamorphosing and metamorphosed animals, and metamorphosis-arrested larvae which had been treated with goitrogens, were examined using anti-human TSH beta and anti-bullfrog LH beta sera. The immunoreactive TSH cells in the goitrogen-treated larvae began to exceed those in the controls in number at 40 days after hatching (stage 64). At the end of this experiment (220 days after hatching), the goitrogen-treated larvae had four times more immunoreactive TSH cells than the controls. The immunoreactive TSH cells in the goitrogen-treated larvae came to occupy nearly the whole area of the section of the pars distalis. Contrary to this, no significant differences were observed in the number of immunoreactive GTH cells between the goitrogen-treated larvae and the controls during their ontogeny. The number of immunoreactive GTH cells was much less than that of immunoreactive TSH cells. Immunocytochemistry at the electron microscopical level revealed many "thyroidectomy cells" with extraordinarily inflated ER and secretory granules which showed strong immunoreactivity with anti-TSH beta antibody only in the pars distalis of the goitrogen-treated larvae. These results suggest the possibility that TSH induces precocious testicular development and maturation in the goitrogen-treated larvae in H. retardatus.