Postnatal involution of the human adrenal fetal zone: Stereologic description and apoptosis

During the first weeks of postnatal development the fetal zone (FZ) of the human adrenal cortex rapidly disappears. Present studies aimed to describe cellular aspects of this involution and to correlate them with apoptosis. A drenals of 38 newborns and infants (aged 1-240 days) were obtained from aut opsies due to accidental death. Postnatal decrease in the adrenal gland wei ght may be divided into 2 distinct phases: rapid one lasting from the birth till the end of the second week of life, and followed by a slower one. Thi s decrease is highly correlated with the decrease of both: the volume of FZ and quantity of its cells. During the whole investigated period, volume of the FZ decreases from 8,017 to 248 mm(3) (from 70 to 3% of total adrenal v olume) and the quantity of its parenchymal cells from 3x10(9) to 0.15x10(9) (from 40 to 5% of all parenchymal cells). The average volume of the FZ cel l decreases from 2,200 to 1,400 mu m(3). The volume of FZ stroma (connectiv e tissue and blood vessels) expands notably during the first day and decrea ses from day 5th of life. The apoptotic index of the FZ parenchymal cells i s the highest during the second week of life (ca 30%), and subsequently dec lines (ca 20%). Thus, the rapid involution of the FZ is connected with mark ed hemorrhagic changes and increased apoptotic index of parenchymal cells, while during the slow phase (after 2nd week on) apoptotic index is lower an d rather constant.