2. THE NEUROHYPOPHYSIS
173
This teleost neurophysin was acidic and rich in cystine, and it appeared
to have a greater capacity for arginine vasotocin than for mammalian
arginine vasopressin.
It can be concluded that the neurohypophyses of all the teleosts investigated so far appear to contain arginine vasotocin and 4 Ser, 8 Ile
oxytocin. However, the number of species studied is minute compared
with the approximately 20,000 species which exist in this highly diversified
group (Dodd et al., 1966). It is possible that isolated mutations could
have resulted in the production of other active peptides, but so far none
of these has been demonstrated.
C. The Actions of the Neurohypophysial Principles in the Teleosts
Until recently, the functions of the neurohypophysial principles in the
teleost fish received only sporadic attention, and the majority of studies
utilized mammalian principles. Although the information available is unsatisfying, it is beginning to suggest that the peptides are concerned in
at least two main fields-in
osmoregulation-salt balance and in
reproduction.
The earliest indications of an importance in osmoregulation came from
the considerable body of histological evidence which suggested that there
was a depletion of neurosecretory materials from the neurohypophysis of
freshwater and marine fish when they were immersed in saline which was
hypertonic to their previous environment ( Callionymus lyra, Ammodytes
lanceolatus, Arvy and Gabe, 1954; Phoxinus laeuis, Arvy et al., 1959;
Gasterosteus aculeatus, Fridberg and Olsson, 1959; etc. ). Lederis ( 1963)
has shown that this is accompanied by the emptying of elementary vesicles,
as seen in Salmo irideus with the electron microscope. Also, he carried
out parallel oxytocic and pressor assays, which suggested that there was
depletion of arginine vasotocin, but not of 4 Ser, 8 Ile oxytocin. This is
corroborated by Carlson and Holmes (1962), who observed that the
transfer of Salmo gairdneri from freshwater to saltwater resulted in an
initial fall in the antidiuretic activity of the pituitary, while the oxytocic
content tended to increase. All hormonal levels had returned to normal
within 6 hr. Not all fish show these changes clearly; Anguilla anguilla
appears to be relatively insensitive to changes in salinity, as judged by
these histological criteria (Arvy et al., 1959, Leatherland and Dodd,
1969b). The transfer or return of fish to hypotonic conditions may result
in the expected accumulation of neurosecretory material in the neurohypophysis, as in Callion ymus lyra, Ammodytes lanceolutus, and Phoxinus
laevis ( Arvy and Gabe, 1954; Fontaine, 1956) ; but Gasterosteus aculeatus
173
This teleost neurophysin was acidic and rich in cystine, and it appeared
to have a greater capacity for arginine vasotocin than for mammalian
arginine vasopressin.
It can be concluded that the neurohypophyses of all the teleosts investigated so far appear to contain arginine vasotocin and 4 Ser, 8 Ile
oxytocin. However, the number of species studied is minute compared
with the approximately 20,000 species which exist in this highly diversified
group (Dodd et al., 1966). It is possible that isolated mutations could
have resulted in the production of other active peptides, but so far none
of these has been demonstrated.
C. The Actions of the Neurohypophysial Principles in the Teleosts
Until recently, the functions of the neurohypophysial principles in the
teleost fish received only sporadic attention, and the majority of studies
utilized mammalian principles. Although the information available is unsatisfying, it is beginning to suggest that the peptides are concerned in
at least two main fields-in
osmoregulation-salt balance and in
reproduction.
The earliest indications of an importance in osmoregulation came from
the considerable body of histological evidence which suggested that there
was a depletion of neurosecretory materials from the neurohypophysis of
freshwater and marine fish when they were immersed in saline which was
hypertonic to their previous environment ( Callionymus lyra, Ammodytes
lanceolatus, Arvy and Gabe, 1954; Phoxinus laeuis, Arvy et al., 1959;
Gasterosteus aculeatus, Fridberg and Olsson, 1959; etc. ). Lederis ( 1963)
has shown that this is accompanied by the emptying of elementary vesicles,
as seen in Salmo irideus with the electron microscope. Also, he carried
out parallel oxytocic and pressor assays, which suggested that there was
depletion of arginine vasotocin, but not of 4 Ser, 8 Ile oxytocin. This is
corroborated by Carlson and Holmes (1962), who observed that the
transfer of Salmo gairdneri from freshwater to saltwater resulted in an
initial fall in the antidiuretic activity of the pituitary, while the oxytocic
content tended to increase. All hormonal levels had returned to normal
within 6 hr. Not all fish show these changes clearly; Anguilla anguilla
appears to be relatively insensitive to changes in salinity, as judged by
these histological criteria (Arvy et al., 1959, Leatherland and Dodd,
1969b). The transfer or return of fish to hypotonic conditions may result
in the expected accumulation of neurosecretory material in the neurohypophysis, as in Callion ymus lyra, Ammodytes lanceolutus, and Phoxinus
laevis ( Arvy and Gabe, 1954; Fontaine, 1956) ; but Gasterosteus aculeatus