The embryological development and cytodifferentiation of the pars distalis of the golden hamster (Mesocricetus auratus). A light and electron microscopic study.

The embryological development of cytodifferentiation of the hamster pars distalis was investigated using light and electron microscope techniques in order to obtain basic information for comparison with pituitary development in other mammalian species. The normal chronological events in the development of the hamster pars distalis closely paralleled the pituitary organogenesis of other laboratory rodents. Rathke's pouch formed and touched the infundibulum at 8 1/2 days of gestation and separated from the stomodeum 3 days later. Penetration of vascular elements from the developing hypophysial portal system into the pars distalis occurred at 12 1/2 days gestation. This was also the first day that small secretory granules were seen in any of the parenchymal cells. Further cytodifferentiation during the following prenatal, and first few postnatal days of life revealed granulated cells which, in most cases, could not be identified using morphological criteria or granule size as may be done in the adult. An orderly sequence of inductive and morphological events appears to take place in the developing hamster adenohypophysis paralleling similar events observed in other animals.