The view is consistent with observations reported recently that Sonic hedgehog (Shh), an important factor in embryonic development and adult stem cell maintenance, exists in zU of the rat adrenal gland and the Shh-containing cells seem to migrate bidirectionally. We proposed that cells in and around zU are stem/progenitor cells of the rat adrenal cortex, maintaining functional zonation of the adrenal cortex.

The adrenal gland secretes a handful of hormones to achieve all. The entire gland is wrapped in a protective adipose. The purpose of the adrenal glands is to regulate body metabolism, immunity, blood pressure, and different bodily functions. Further, BrdU (5-bromo-2′-deoxyuridine)-incorporating cells (cells in S-phase) were concentrated at the outer region and the inner region of zU, and these cells proliferated and migrated bidirectionally: toward zG centrifugally and toward zF centripetally. The cortex also plays an important role in the adrenal glands function by creating stress hormones.

The zone appeared to be devoid of any significant endocrine functions specific to adrenocortical zones, therefore, we designated the zone as “undifferentiated cell zone (zU)”. The following points highlight the four main endocrine functions of adrenal cortex. In 1994, we identified immunohistochemically a new zone between zG and zF of the rat adrenal gland.

The adrenal cortex of mammals consists of three concentric zones, i.e., the zona glomerulosa (zG), the zona fasciculata (zF), and the zona reticularis (zR), which secrete mineralocorticoids, glucocorticoids, and adrenal androgens, respectively.

Function of adrenal cortex