1. THE PITUITARY GLAND
21
microscope. Fundulus heteroclitus also has typical e cells, in a palisade
behind the 7 cells. Sokol (1961) described them as blue-green basophils
(after aldehyde fuchsin-light green-orange G ) ; and they also display the
characteristic affinities for erythrosin, Alizarin blue, and PbH (Ball,
1967). Sokol also described the E cells of the guppy, Poecilia reticuhtu,
as weakly staining green basophils.
At the ultrastructural level, the eel E cell reveals a moderately electron
dense cytoplasm containing numerous fine vesicles or microtubules. The
endoplasmic reticulum is diffuse and not prominent, and the Golgi area
is rarely seen in normal fish. The cytoplasm is evenly packed with electron
dense granules measuring 200-250 mp in diameter (Knowles and Vollrath, 1966b). Follenius (1963a) described the cells as forming a chromophobic band in several teleosts, and his ultrastructural studies revealed a
sparse cytoplasm with ergastoplasmic vesicles in some cells; other cells
contained a well-developed Golgi apparatus surrounded by osmiophilic
secretory granules.
The most general point of agreement in the various accounts is that
these cells tend toward chromophobia, especially marked in cyprinodonts.
This tendency may be exaggerated by stress at sacrifice, when the animal
may struggle, or by prolonged anesthesia (Olivereau, 196%). A similar
tendency toward chromophobia is characteristic of the ACTH cell in
higher vertebrates (cf. Racadot, 1963b; Kraicer et al., 1967).
Evidence for t h Secretion of ACTH by the E CeUs. Allocation of
ACTH secretion to these cells was accomplished simultaneously and independently by treatment of P . latipinnu and Anguillu with Metopirone
(SU 4885 Ciba, metyrapone), a drug which inhibits the biosynthesis of
adrenocorticosteroids. Although other actions have been described, its
main effect in mammals, following short-term treatment with low doses,
is inhibition of llp-hydroxylase, thus preventing the formation of the
normal 11-oxycorticosteroids. As a result, because of the negative feedback relationship between these steroids and ACTH, the use of SU 4885
has led to identification of the ACTH cells of mammals and birds (see
Ball and Olivereau, 1966; Kraicer et al., 1967).
In Poecilia and the eel, short-term treatment with SU 4885 resulted in
hypertrophy and hyperplasia of the interrenal cells, indicating increased
ACTH secretion, and this was accompanied specifically by activation of
only the c cells in the pituitary (Olivereau and Ball, 1963; Ball and
Olivereau, 1966). This morphological stimulation of the interrenal by the
drug is partly (eel) or wholly (Poecilia) suppressed by hypophysectomy,
which supports the interpretation that SU 4885 elicits elevated ACTH
output and hence identifies the E cells as corticotrops (Figs. 12 and 13).
With longer treatment in both species the TSH cells are stimulated, along
21
microscope. Fundulus heteroclitus also has typical e cells, in a palisade
behind the 7 cells. Sokol (1961) described them as blue-green basophils
(after aldehyde fuchsin-light green-orange G ) ; and they also display the
characteristic affinities for erythrosin, Alizarin blue, and PbH (Ball,
1967). Sokol also described the E cells of the guppy, Poecilia reticuhtu,
as weakly staining green basophils.
At the ultrastructural level, the eel E cell reveals a moderately electron
dense cytoplasm containing numerous fine vesicles or microtubules. The
endoplasmic reticulum is diffuse and not prominent, and the Golgi area
is rarely seen in normal fish. The cytoplasm is evenly packed with electron
dense granules measuring 200-250 mp in diameter (Knowles and Vollrath, 1966b). Follenius (1963a) described the cells as forming a chromophobic band in several teleosts, and his ultrastructural studies revealed a
sparse cytoplasm with ergastoplasmic vesicles in some cells; other cells
contained a well-developed Golgi apparatus surrounded by osmiophilic
secretory granules.
The most general point of agreement in the various accounts is that
these cells tend toward chromophobia, especially marked in cyprinodonts.
This tendency may be exaggerated by stress at sacrifice, when the animal
may struggle, or by prolonged anesthesia (Olivereau, 196%). A similar
tendency toward chromophobia is characteristic of the ACTH cell in
higher vertebrates (cf. Racadot, 1963b; Kraicer et al., 1967).
Evidence for t h Secretion of ACTH by the E CeUs. Allocation of
ACTH secretion to these cells was accomplished simultaneously and independently by treatment of P . latipinnu and Anguillu with Metopirone
(SU 4885 Ciba, metyrapone), a drug which inhibits the biosynthesis of
adrenocorticosteroids. Although other actions have been described, its
main effect in mammals, following short-term treatment with low doses,
is inhibition of llp-hydroxylase, thus preventing the formation of the
normal 11-oxycorticosteroids. As a result, because of the negative feedback relationship between these steroids and ACTH, the use of SU 4885
has led to identification of the ACTH cells of mammals and birds (see
Ball and Olivereau, 1966; Kraicer et al., 1967).
In Poecilia and the eel, short-term treatment with SU 4885 resulted in
hypertrophy and hyperplasia of the interrenal cells, indicating increased
ACTH secretion, and this was accompanied specifically by activation of
only the c cells in the pituitary (Olivereau and Ball, 1963; Ball and
Olivereau, 1966). This morphological stimulation of the interrenal by the
drug is partly (eel) or wholly (Poecilia) suppressed by hypophysectomy,
which supports the interpretation that SU 4885 elicits elevated ACTH
output and hence identifies the E cells as corticotrops (Figs. 12 and 13).
With longer treatment in both species the TSH cells are stimulated, along