SOME ASPECTS OF ZONATION AND FUNCTION OF THE ADRENAL CORTEX

SUMMARY The adrenal of male and female rats with persistent diabetes insipidus showed a prominent zona fasciculata and zona reticularis. The zona glomerulosa was narrow or absent. The results from this and the preceding three papers are here reviewed together. It is concluded that control of salt-electrolyte metabolism cannot be ascribed to the zona glomerulosa. It is probable that the zona fasciculata is reponsible for most of the adrenocortical secretions. The zona glomerulosa is a vegetative back-water of cells, which is able to produce minimal amounts of adrenocortical secretions without stimulation by pituitary hormones, but is only of significance when the latter are absent. Rising amounts of circulating adrenocorticotrophic hormone (ACTH) can transform the zona glomerulosa into actively secreting cells of the zona fasciculata type. After cessation of such activity the zona glomerulosa re-forms, as the amount of ACTH will maintain only a certain volume of zona fasciculata (and zona reticularis) against the rigid limiting inner circumference formed by the medulla; some of the cells derived from the chief area of cell division in the outer part of the zona fasciculata do not mature to cells of the zona fasciculata type, but form zona glomerulosa cells. It is thought that cell migration occurs from the cells of the outer region of the zona fasciculata to the zona reticularis and that this is, normally, a slow process.