1. THE PITUITARY GLAND
17
Olivereau, 1968), although the adrenal inhibitor SU 4885 leads to slight
and irregular stimulation of these cells (Olivereau, 1965). Given over
three days, ACTH inactivated the prolactin cells of Hippocumpus (Boisseau, 1967). The only indications of gonadal influences on these cells are
Olivereau’s observation ( 1967a) that in freshwater the prolactin cells are
more active in female than in the male eels (immature fish), and Sokol’s
report (1961) that the r] cells of F. heteroclitus undergo a transient chromophobia ( = partial degranulation) coincident with spawning in the
coastal seawater.
Like the mammalian prolactin cell, the r] cell in Poecilia remains active
in ectopic pituitary transplants, an activity manifested both functionally
(tolerance of freshwater, Ball et ul., 1965; Ball and Olivereau, 1965;
reduction of sodium turnover in dilute seawater, Ball and Ensor, 1968)
and cytologically (Olivereau and Ball, 1966; Ball and Olivereau, 1965).
In such transplants, as in the normal gland (Ball, 1969), the r] cells are
activated rapidly when the fish enters freshwater from dilute seawater
(Ball and Olivereau, 1965). Thus hypothalamic connections are not
essential for activation of the r] cells in response to salinity reduction, nor
for the maintenance of their activity in freshwater. However, we are not
in a position to postulate a hypothalamic prolactin-inhibiting factor (PIF)
such as exists in mammals (Meites and Nicoll, ISSS), since we do not
yet have quantitative data on secretory rates of fish prolactin from transplants and from the in situ gland (cf. Olivereau and Ball, 1!366). It is
difficult, because of this, to interpret Olivereau’s observations that prolonged treatment with ovine prolactin leads to regression of the r] cells of
Anguilla ( Ball and Olivereau, 1964; Olivereau, 1969c), and Boisseau’s
finding (1967) that a three-day treatment with prolactin led to marked
involution of Hippocampus r] cells. Comparable physiological observations in the rat are suggestive of an increase in secretion of PIF induced
by the exogenous prolactin, leading to inhibition of endogenous prolactin
output (Clemens and Meites, 1968), but obviously this concept may not
be extended to teleosts in the present state of our knowledge.
In vitro observations agree with the results from pituitary transplants,
the 77 cells remaining active in cultured trout glands, with partial or total
degranulation and cellular enlargement ( Baker, 1963a). In cultured
glands from Fundulus heteroclitus, Emmart and Mossakowski (1967)
found that new colonies of r] cells, arising by mitoses in the outgrowing
layers of the explant, contained granules that bound a fluorescent antibody to sheep prolactin, indicating the continued ability of the 77 cells to
synthesize fish prolactin in the complete absence of hypothalamic influences. Fixed material from these cultures showed evidence of release
of fluorescent-labeled granules across the cell surfaces (cf. Weiss, 196.5,
17
Olivereau, 1968), although the adrenal inhibitor SU 4885 leads to slight
and irregular stimulation of these cells (Olivereau, 1965). Given over
three days, ACTH inactivated the prolactin cells of Hippocumpus (Boisseau, 1967). The only indications of gonadal influences on these cells are
Olivereau’s observation ( 1967a) that in freshwater the prolactin cells are
more active in female than in the male eels (immature fish), and Sokol’s
report (1961) that the r] cells of F. heteroclitus undergo a transient chromophobia ( = partial degranulation) coincident with spawning in the
coastal seawater.
Like the mammalian prolactin cell, the r] cell in Poecilia remains active
in ectopic pituitary transplants, an activity manifested both functionally
(tolerance of freshwater, Ball et ul., 1965; Ball and Olivereau, 1965;
reduction of sodium turnover in dilute seawater, Ball and Ensor, 1968)
and cytologically (Olivereau and Ball, 1966; Ball and Olivereau, 1965).
In such transplants, as in the normal gland (Ball, 1969), the r] cells are
activated rapidly when the fish enters freshwater from dilute seawater
(Ball and Olivereau, 1965). Thus hypothalamic connections are not
essential for activation of the r] cells in response to salinity reduction, nor
for the maintenance of their activity in freshwater. However, we are not
in a position to postulate a hypothalamic prolactin-inhibiting factor (PIF)
such as exists in mammals (Meites and Nicoll, ISSS), since we do not
yet have quantitative data on secretory rates of fish prolactin from transplants and from the in situ gland (cf. Olivereau and Ball, 1!366). It is
difficult, because of this, to interpret Olivereau’s observations that prolonged treatment with ovine prolactin leads to regression of the r] cells of
Anguilla ( Ball and Olivereau, 1964; Olivereau, 1969c), and Boisseau’s
finding (1967) that a three-day treatment with prolactin led to marked
involution of Hippocampus r] cells. Comparable physiological observations in the rat are suggestive of an increase in secretion of PIF induced
by the exogenous prolactin, leading to inhibition of endogenous prolactin
output (Clemens and Meites, 1968), but obviously this concept may not
be extended to teleosts in the present state of our knowledge.
In vitro observations agree with the results from pituitary transplants,
the 77 cells remaining active in cultured trout glands, with partial or total
degranulation and cellular enlargement ( Baker, 1963a). In cultured
glands from Fundulus heteroclitus, Emmart and Mossakowski (1967)
found that new colonies of r] cells, arising by mitoses in the outgrowing
layers of the explant, contained granules that bound a fluorescent antibody to sheep prolactin, indicating the continued ability of the 77 cells to
synthesize fish prolactin in the complete absence of hypothalamic influences. Fixed material from these cultures showed evidence of release
of fluorescent-labeled granules across the cell surfaces (cf. Weiss, 196.5,