Immunohistochemical identification of prolactin-producing cells in the mouse adenohypophysis.

Abstract

Prolactin producing cells in the anterior pituitary glands of normal adult male and female mice were observed immunohistochemically using anti-mouse prolactin rabbit serum. In this study, three types of prolactin cells can be distinguished. The first type contains small spherical secretory granules about 100 nm in diameter, the second type has medium sized spherical secretory granules ranging in diameter from 150 to 200 nm, and the third type has secretory granules, about 300 nm in maximal diameter, in variable shapes and sizes. The shapes of prolactin cells vary from oval, polygonal, stellate to cup-shaped. The Type I and Type III prolactin cells are usually oval or polygonal, but the Type II prolactin cells are mostly irregular. In the Type I and Type II prolactin cells, the cytoplasmic organellae are poorly developed. However, the Type III prolactin cells have well developed endoplasmic reticula and enlarged Golgi apparatus. The Type III prolactin cells are most likely the same as the anterior hypophysial cells described as mammotrophs or lactotrophs by earlier investigators using morphological criteria. However, the Type I and Type II cells identified by the present immunohistochemical study using anti-mouse prolactin rabbit serum have never previously been recognized as prolactin cells by non-immunohistochemical methods. Sex differences are observed in the proportion and the frequency of the occurrence of these three types of prolactin cells in the anterior pituitary gland of the mouse: among three types of prolactin cells, the most predominant type being Type III in female mice, whereas Type II in male mice.