A NOVEL CELL LAYER WITHOUT CORTICOSTEROID-SYNTHESIZING ENZYMES IN RATADRENAL-CORTEX - HISTOCHEMICAL DETECTION AND POSSIBLE PHYSIOLOGICAL-ROLE

A stratum of cells that did not contain both aldosterone synthase cyto chrome P450 (cytochrome P450aldo) and cytochrome P45011 beta was found immunohistochemically between the tons glomerulosa and the zona fasci culata of the rat adrenal cortex. As cytochromes P450aldo and P45011 b eta are the enzymes responsible for the biosynthesis of aldosterone an d corticosterone, respectively, the cells there are considered to be i ncapable of synthesizing both aldosterone and corticosterone. Furtherm ore, the cells are regarded as inert in producing adrenal androgens, b ecause rat adrenal cortex is known to lack steroid 17 alpha-hydroxylas e. Thus, the stratum is composed of cells that do not syn thesize any of the major corticosteroids in significant quantities. It was 5-10 ce lls thick under normal feeding conditions, but diminished to 4-5 cells thick when animals were maintained under Na restriction, which is kno wn to stimulate the secretion of angiotensin-II. When the distribution of 5-bromo-2'-deoxyuridine-labeled nuclei in the adrenocortex from Br dU-administered rats was examined, the stained nuclei were concentrate d in and around the cell stratum. The pulse-chase experiments showed t hat the labeled cells migrated out of this layer and into the zonae fa sciculata-reticularis. On the basis of these findings, we suggest that the newly discovered cell layer is the progenitor cell zone of the ra t adrenal cortex.