Immunocytochemical Studies on the Cytodifferentiation of the Adenohypophysis of the Golden Hamster

Abstract

The differentiation of the adenohypophysial cells in the developing golden hamster was studied immunocytochemically to determine their time of the first appearance, localization, and change in the distribution during development in connection with development of hypothalamo-hypophysial system. The cells of Atwell's process at day 11 of gestation showed first immunopositive reaction to anti-rat LH and anti-ovine LHβ sera. ACTH-, LH-, and TSH-immunoreactive cells first appeared simultaneously in the midventral portion of the pars distalis at day 12.5 of gestation. They were independent types of cells showing peculiar forms and distributions. FSH-immunoreactive cells appeared first in a small number in the ventral portion of the pars distalis at day 14 of gestation. Some FSH cells also showed immunopositive reaction to anti-rat LH and anti-ovine LHβ sera. GH-immunoreactive cells appeared first in the caudal part of the pars distalis at day 15 of gestation, while PRL-immunoreactive cells occurred in the central portion of the pars distalis at 3 days after birth. The pars tuberalis was originated from Atwell's process at day 12.5 of gestation and contained LH- and LHβ-immunoreactive cells but not other types of pituitary cells. In the hypothalamus, LHRH-immunoreactive perikarya appeared first in the preoptic nucleus and somatostatin-positive cells occurred in the arcuate nucleus at day 12.5 of gestation. The vascularization of the pars distalis via the Atwell's recess occurred at day 12 of gestation.