16. ACTIONS OF HORMONES
603
in medium containing pituitary extract was found to inactivate
thyrotrophin (Rawson, Sterne and Aub, 1942).
The changes seen in culture closely resemble those obtained by De
Robertis (1942) in rat and guinea-pig thyroids in vivo except that the
colloid was not taken up by macrophages, since in the organism it was
released into the circulation. Junqueira found that, in thyroid glands
pretreated with iodide, the action of the hormone was strongly inhibited
and that both secretion and release of the colloid were suppressed. In
his view this inhibition is either due to a blocking of the enzymatic
system on which thyrotrophin acts or to a direct chemical inter-action
with the hormone. Direct inhibition of proteolytic enzymes by iodide
in vitro has been demonstrated by De Robertis and Nowinski (1946).
B. EFFECT OF ACTH ON THE ADRENAL CORTEX
Two main regions of the adrenal cortex were studied: the zona
glomerulosa, consisting of small crowded cells without apparent
organization; and the zona fasciculata, which is the source of glucocorticosteroids and is composed of large vacuolated cells arranged
in radially orientated cords. Experiments on hypophysectomized rats
have shown (Deane and Greep, 1946) that the glomerulosa cells are
independent of the presence of the pituitary; they are not influenced
by small doses of A C T H but, if exposed to high concentrations, can
differentiate into fasciculata cells (Bergner and Deane, 1948). In
contrast, the zona fasciculata depends on the presence of A C T H .
In adrenal glands from 5-day rats, explanted into medium without the
hormone, the zona fasciculata degenerates and is replaced by cells
from near the capsule which differentiate into glomerulosa cells
(Schaberg, 1955, 1957). Addition of A C T H (0-2-2 i.u. per ml medium)
prevented this degeneration and at the higher doses increased the
amount of cytoplasm which often became vacuolated. In some cells
the vacuoles enlarged and became filled with a colloid-like material.
Occasionally, they ruptured and became confluent with those of
the neighbouring cells. A similar effect, maintenance of the zona
fasciculata with enlargement of the cytoplasm and increased vacuolation,
was seen in adrenal gland explants grown in contact with fragments
of anterior pituitary glands from animals of the same age as the adrenal
cultures. The magnitude of the effect depended on the distance
between the two tissues and was greatest in areas directly adjacent to
the pituitary gland. In this region the effect closely resembled that
brought about by high doses of A C T H , and also corresponded to that
described by Selye and Stone (1950) in rats treated with crude extracts
of anterior pituitary gland.
603
in medium containing pituitary extract was found to inactivate
thyrotrophin (Rawson, Sterne and Aub, 1942).
The changes seen in culture closely resemble those obtained by De
Robertis (1942) in rat and guinea-pig thyroids in vivo except that the
colloid was not taken up by macrophages, since in the organism it was
released into the circulation. Junqueira found that, in thyroid glands
pretreated with iodide, the action of the hormone was strongly inhibited
and that both secretion and release of the colloid were suppressed. In
his view this inhibition is either due to a blocking of the enzymatic
system on which thyrotrophin acts or to a direct chemical inter-action
with the hormone. Direct inhibition of proteolytic enzymes by iodide
in vitro has been demonstrated by De Robertis and Nowinski (1946).
B. EFFECT OF ACTH ON THE ADRENAL CORTEX
Two main regions of the adrenal cortex were studied: the zona
glomerulosa, consisting of small crowded cells without apparent
organization; and the zona fasciculata, which is the source of glucocorticosteroids and is composed of large vacuolated cells arranged
in radially orientated cords. Experiments on hypophysectomized rats
have shown (Deane and Greep, 1946) that the glomerulosa cells are
independent of the presence of the pituitary; they are not influenced
by small doses of A C T H but, if exposed to high concentrations, can
differentiate into fasciculata cells (Bergner and Deane, 1948). In
contrast, the zona fasciculata depends on the presence of A C T H .
In adrenal glands from 5-day rats, explanted into medium without the
hormone, the zona fasciculata degenerates and is replaced by cells
from near the capsule which differentiate into glomerulosa cells
(Schaberg, 1955, 1957). Addition of A C T H (0-2-2 i.u. per ml medium)
prevented this degeneration and at the higher doses increased the
amount of cytoplasm which often became vacuolated. In some cells
the vacuoles enlarged and became filled with a colloid-like material.
Occasionally, they ruptured and became confluent with those of
the neighbouring cells. A similar effect, maintenance of the zona
fasciculata with enlargement of the cytoplasm and increased vacuolation,
was seen in adrenal gland explants grown in contact with fragments
of anterior pituitary glands from animals of the same age as the adrenal
cultures. The magnitude of the effect depended on the distance
between the two tissues and was greatest in areas directly adjacent to
the pituitary gland. In this region the effect closely resembled that
brought about by high doses of A C T H , and also corresponded to that
described by Selye and Stone (1950) in rats treated with crude extracts
of anterior pituitary gland.