The cell types in the rat anterior pituitary were classified according to the function of hormone produced by each type cells. Depending upon the age and sex of the rat studied, the fine structure of the cell remarkably differs from each other. The name of cell type indicates the name (abbreviation) of hormone produced by each type cell, which is also divided into two or three subtypes according to the ultrastructure or developing stage viz. immature, intermediate and mature types. The immunocytochemistry is a useful method both for light and electron microscopy in order to study the activity of every cell organelles, because it is easy to indicate the localization of hormones in the cell. The anterior pituitary hormones are all proteins or polypeptides fragmented from the former, and making antibodies of these hormones is rather easy. Significance of every cell organelles in the endocrine function was clarified.


(Communicated by Kiyoshi HAMA, M.J.A.)