LOCALIZATION OF P450ALDO AND P45011-BETA IN NORMAL AND REGENERATING RAT ADRENAL-CORTEX

A novel layer of cells that do not contain both P450aldo and P45011 be ta has been discovered between the zonae glomerulosa and fasciculata o f the rat adrenal cortex. Since P450aldo and P45011 beta are the enzym es responsible for the formation of aldosterone and corticosterone, re spectively, the cells in that zone are presumably inert in synthesizin g both aldosterone and corticosterone, in other words, the layer is co mposed of cells that have no zone-specific endocrine function as an ad renocortical component. Cytologically, the layer consists of tightly p acked cells, which contain a lesser amount of lipid droplet than the c ells in the other zones, and appears as a white ring or a white zone i n the double immunostaining with anti P450aldo and anti P45011 beta. U pon angiotensin II-stimulation evoked by Na-deficiency, the number of the zona glomerulosa cells expressing P450aldo increases for the initi al 2 or 3 days and then the P450aldo-containing zona glomerulosa cells begin to proliferate. Thus angiotensin II serves as a proliferator of the zona glomerulosa cells of the rat adrenal cortex. During the peri od, the thickness of the white zone decreases for initial 3 days and b ecomes constant after 5 or 6 days, being about 5 % of the total cell n umber of the adrenal cortex. When localization of replicating cells wa s examined in the adrenal cortex, they were found to be concentrated i n and around the white zone. Then the pulse-chase experiments with Brd U showed that the labeled cells migrated out of the white zone and int o the zonae fasciculata and reticularis. The localization of the repli cating cells in the regenerating adrenal cortex was also around the re gion between the zonae glomerulosa and fasciculata. On the basis of th ese findings, we suggest that the newly discovered cell layer (the whi te zone) is the stem cell zone of the rat adrenal cortex.