Histological and ultrastructural studies of the rabbit pars intermedia in organ culture. I. Adult and young adult tissue.

Fuuly differentiated rabbit pars intermedia has been maintained successfully for over six weeks as organ culture. PI-glandular cells are the commonest type throughout the culture. They retain their differential condition for at least five weeks. Autoradiography indicates that cell division occurs in cultures for at least two weeks. Dense granules are seen in the intercellular, perivascular and vascular spaces and are taken to indicate secretory activity under the conditions of culture. Some interstitial cells remain recognisable throughout the culture and ACT-type cells for more than two weeks. Other interstitial cells lose their usual appearance and become peripheral dark cells. Modification of cytoplasmic organelles, including distortion and darkening of mitochondria, increase in intracellular filaments and enlargement and liberation of the content of the PI-vesicles are reported.