Prenatal development of the adrenal in pig Sus scrofa dom. Part II. Adrenal cortex development in the second part of pregnancy

Abstract

The development of the adrenal cortex in pig fetuses between the 50 and 112 day of pregnancy were investigated with histological and histochemical methods and in electron microscope. Three consecutive generations of the cortical cells were observed. They had features of steroidogenic cells and differed with mature of mitochondria and in amount of SER and in enzyme activity. The earliest differentiated fetal cortical cells demonstrated alkaline phosphatase activity and giant mitochondria. They were translocated from the periphery to the center of the adrenal, where they degenerated and disappeared in the late pregnancy. The second generation--transitional cortical cells appeared about 70 day of development. They have pleomorphic mitochondria and abundant SER and low alkaline phosphatase activity. The last generation--the definitive cortical cells differentiated from 100 day of development and their number increased till the parturition. They had active 3-beta-hydroxysteroid dehydrogenase, spherical mitochondria and characteristic concentric whorls of SER. A probable role of the three generations of cortical cells is was discussed. In the subcapsular region of fetal adrenal undifferentiated and differentiating cells were observed, forming glomerularlike groups. Their role in the formation of cortical blastema and future zona glomerulosa was discussed. In the first part of the studies the formation of the mesenchymal primordium of the adrenal cortex was examined in early fetuses of domestic pig, and then differentiation of mesenchymal cells into steroidogenic cortical cells. The changes encountered then at the ultrastructural level consisted of an increased area of SER and greater number of mitochondria. At the same time, the shape of mitochondria altered and the cristae from lamellar became tubular. In the period around 50 day of development fetal adrenal was already a separate organ, with a capsule, composed of cords of fetal cortical cells divided by the blood vessels and strands of chromaffinoblasts penetrating the adrenal. Fetal cortical cells were characterized by alkaline phosphatase activity. The following study presents farther development of the adrenal cortex till the time of birth.