200 J. J. Christian 



hydrocortisone and cortisone (ll-oxy-17-hydroxycorticoids). Corticoste- 

 rone is included in this latter group, although it has moderate effects on 

 both salt-electrolyte and carbohydrate metabolism. It is considerably 

 weaker in all these actions than the principal corticoids in either of the 

 categories (Jones, 1957). This classification into primarily carbohydrate- 

 active and primarily sodium-retaining corticoids is useful, but by no means 

 does it reflect the entire spectrum of activities of the hormones; in many 

 instances there is a considerable overlap in these activities for a particular 

 hormone, for example, corticosterone. 



Recent morphologic and direct evidence shows that the secretion of 

 aldosterone is a function of the zona glomerulosa, whereas the carbohy- 

 drate-active corticoids, except corticosterone, and probably the C19 steroids 

 are secreted by the zona fasciculata and zona reticularis. Probably the 

 most conclusive evidence for the relationship between specific secretory 

 function and zonation of the adrenal cortex has been provided by the in 

 vitro incubation and determination of the secretory products of selected 

 segments of the adrenal cortex. Aldosterone was found to be secreted only 

 by incubated portions of the zona glomerulosa of the adrenals of rats and 

 beef cattle (Ayres et al., 1956; Giroud et al., 1956; Giroud et at., 1958); 

 hydrocortisone was produced only by the zonae fasciculata-reticularis, and 

 corticosterone was produced at approximately equal rates by all three 

 zones of the adrenals of beef cattle (Ayres et al., 1956; Giroud ct al., 1958 

 Stachenko and Giroud, 1959a, b) . It was also shown in these experiments 

 that ACTH or corticotropin peptides or other steroids were without effect 

 on the production of aldosterone by the zona glomerulosa but that they 

 markedly increased the production of total corticosteroids and of hydro- 

 cortisone by the fasciculata-reticularis (Stachenko and Giroud, 1959b). 

 Additional evidence of functional zonation, less direct, has been obtained 

 by relating changes in the composition of the secretory product with mor- 

 phologic changes in the various zones of the adrenal cortex. A sodimn- 

 deficient diet produces extreme hypertrophy of the zona glomerulosa and 

 atrophy of the zona fasciculata of the adrenal cortices of rats (Hartroft and 

 Eisenstein, 1957), and these changes are associated with a marked increase 

 in the secretion of aldosterone and decreases in the secretion of corticoste- 

 rone (Eisenstein and Hartroft, 1957). In somewhat comparable experi- 

 ments it was shown that (1) sodium deprivation markedly increased the 

 aliesterase activity of the zona glomerulosa but had no effect on its activity 

 in the fasciculata of the adrenals of mice; (2) deoxycorticosterone or sodium 

 flooding depressed the aliesterase activity of the zona glomerulosa and 

 increased it in the zona fasciculata; and (3) injected ACTH markedly 

 increased the aliesterase activity of the zona fasciculata but did not affect 

 it in the zona glomerulosa, whereas blocking ACTH secretion with cortisone 



