Differentiation of cells producing polypeptide hormones (ACTH, MSH, LPH, alpha- and beta-endorphin, GH and PRL) in the fetal porcine anterior pituitary.

The aim of the present study on the fetal porcine pituitary was (1) to detect by means of the immunoperoxidase technique the earliest stages of cells producing polypeptide hormones: beta-MSH, ACTH, beta-LPH, alpha- and beta-endorphin, growth hormone (GH) and prolactin (PRL), (2) to study the development of the synthesis and the storage of these hormones during fetal life, and (3) to detect whether several hormones can be located in one and the same cell. The corticotropic cells were revealed as the earliest functional elements of the fetal anterior pituitary. Our results indicate clearly that ACTH, beta-MSH, beta-LPH, alpha- and beta-endorphin appear at 34 days in the same regular, round or ovoid cells; no differences in the time of their appearance could be observed. The ACTH-cells, irregular or angular in shape and endowed with cytoplasmic processes such as described in the adult pituitary, were not seen until day 50. The first GH-cells were detected between 40 to 45 days of fetal life. From day 45 to 90, the GH-cells greatly increased in number and in staining intensity of their progressively extending cytoplasmic area, but they displayed the same regular and round shape. The PRL-cells were the last cell type to appear in the fetal pituitary. The first PRL-cells, small in size and round or ovoid in shape with a high nucleus/cytoplasm ratio, were detected at day 70. At day 80, the PRL-cells increased in size and staining intensity. They displayed an irregular elongated or stellated shape and cytoplasmic processes resembling those characteristic of the adult pituitary.(ABSTRACT TRUNCATED AT 250 WORDS)