Ultrastructural and immunocytochemical studies of prolactin‐secreting cells (PRL cells) in the anterior pituitary gland of the female musk shrew (Suncus murinus L.)

Abstract

Prolactin-secreting cells (PRL cells) in the anterior pituitary gland of the female musk shrew were identified by the protein A-gold procedure combined with electron microscopy. Their secretory granules were spherical, and showed various sizes ranging in diameter from 100 nm to 800 nm according to the difference in physiological conditions of the animals. In pregnant and lactating animals, the PRL cells exhibited morphologically active features, i.e., a large prominent Golgi apparatus and a well-developed rough endoplasmic reticulum (RER) consisting of densely packed parallel lamellae. In pregnant and estrogen-treated animals, the secretory granules of PRL cells significantly increased in size as compared with those of virgin animals. The most remarkable ultrastructural change observed in PRL cells of pregnant, lactating, and estrogen-treated female musk shrews was the occurrence of "intracisternal" granules. They were small and spherical, and were located without limiting membranes inside the dilated cisternae of the RER. Intracisternal granules, as well as ordinary secretory granules, were found to be immunoreactive for PRL by the protein A-gold procedure. These results suggest that PRL cells of the female musk shrew may possibly utilize a "bypass" route to form hormone-containing granules under highly activated cellular conditions.

Immunogold Identification of Prolactin Cells of Goats in Anoestrus, Pregnancy and Milk Production: Ultrastructural Variations

“…above all. at pregnancy, PRL-II cells contain a moderate number of middle-sized and large secretory granules, the largest granules occur at the latter stage as observed by Ishibashi and Shiino [19]. Dannies and Tam [7] stated that when the cell does not secrete at a high rate the hormone remains stored in large granules.…”

Fine structural dynamics showing functional changes of anterior pituitary cells in the rat

“…Colocalization of GH and PRL was also reported in the same cell in a pregnant rat. 29) Because GH and PRL are similar in chemical structure hence some variations may occur in genetic information that is a kind of malformation producing these two hormones in the same single cell. Other substances than the hormones but related in function of secretory granule fomation may colocalize with the normal hormone such as PRL.…”