(i) Homogenates prepared from both fascicular
and reticular zones of the adrenal cortex of man
showed an equal ability to effect lap--
hydroxylation in vitro.
(ii) After in vivo administration of corticotrophin, homogenates of both zones showed an
increase in 11f- hydroxylating activity.
(iii) On incubating slices of both zones,
corticotrophin caused a more marked stimulation of
corticoid secretion from the fascicular than
from the reticular zone slices. The most
pronounced effect was on the production of
(iv) 11(3 -Hydroxyandrostenedione was secreted
by both zones.
(v) Reticular tissue from the gland of a patient
with Cushing's syndrome was significantly more
responsive to corticotrophin in vitro than
similar tissue from a 'normal gland'.
(vi) A greater proportion of the cholesterol
found in the non -stressed adrenal is localized
in the fascicular zone in the cholesteryl ester
form. The free cholesterol level is
approximately the same in both types of tissue.
However, the cholesterol depletion observed after
stress or following corticotrophin administration
appears to be at the expense of the ester form.
From these results, aligned with reports of
other workers, a mode of action of corticotrophin
on the adrenal cortex has been suggested:-
(a) A primary effect, which may involve
mobilization of storage cholesterol by increased
levels of corticotrophin both in the zona
reticularis and at the fasciculata -reticularis
border, resulting in an elevated presentation of
(b) A secondary effect, possibly as a consequence of an adaptation of enzyme systems to
these increased levels of substrate, producing
an elevated steroid metabolizing activity.
B: Comparative Studies on Adrenals of
(i) The rate of hydroxylation of DOC by adrenal
homogenates is generally higher in those glands
possessing a non -fatty cortex.
(ii) There is no apparent relationship between
the rate of 11P- hydroxylation of DOC by the
adrenal, and the reported F/B ratio found in the
adrenal venous effluent of the various species.
(iii) An active 19- hydroxylase enzyme system
has been demonstrated in the non -fatty type of
adrenal gland, especially that of the golden
hamster. 19- Hydroxylation has not yet been
detected in the adult human adrenal cortex,
although it has been observed with foetal adrenal
(iv) The 19- hydroxylase appears to be
associated with the inner regions of the cortex,
whereas the 18- hydroxylase is localized
exclusively in the zona glomerulosa.
(v) SU )4885, known to inhibit 11P- hydroxylation,
also inhibited the 19- hydroxylation reaction in
the golden hamster adrenal.