44
T.A. Marchanî et ai…
GENERAL
INTRODUCTION
In vertebrates, pituitary growth hormone (GH) is the primary regulator
of
somatic growth (Donaldson a£ al., 1979). In teleost fishes, hypophysectomy
has
been shown to result in a large reduction or a cessation of linear growth
Ÿ
in several species, including killifish, Fundulus heteroclitus,
(Pickford,
1957), guppy, Poecilia latipinna, (Ball and Hawkins, 1976), rainbow trout,
Salmo gairdnerii, (Donaldson and McBride, 1967), and catfish, la£ala£aa
melas, (Kayes, 1977a; 1977b), whereas replacement therapy with a purified
preparation of GH results in a resumption of growth in hypopbysectomized
'
animals
(Pickford, 1957; Kayes, 1977a, 1977b). In addition, the exogenous
?
administration of GH preparations to intact fish results in an augmentation
Ï
of growth, as demonstrated in several salmonid species (Komourdjian al al.,
1976; Clarke ag al., 1977; Donaldson al al., 1979), tilapia, Oreochromis
Ï
(Tilapia) mossambicus, (Clarke a£ al., 1977), and common carp, Cyprinus
…
carpio, (Ade1man, 1977). The possible application of various GH preparations
and growth—promoting substances in piscine aquaculture has also been studied
‘
(Donaldson ag al., 1979).
:
Alth0ugh studies in teleost species have established that the pituitary
gland and GH are essential for normal somatic growth, very little is known
,
about the physiology of circulating GH or the neural regulation of GH secre—
Ï
tion in teleosts, in spite of its potential uses in aquaculture° One of the
factors
contributing to this paucity of information has been the lack of a
highly purified preparation of teleost GH suitable for the development and
validation of a specific radioimmunoassay (RIA) for the measurement of circu—
lating levels of GH. Although GH preparations have been obtained from several
teleost species, including tilapia (Farmer ag al., 1976), chum sa1mon, Oncor—
hynchus ka£a, (Wagner ag al., 1983; Kawauchi a£ al., 1985), coho salmon, Q;
kisutch, (Steiny a£ al., 1984), and sturgeon, Acipenser güldenstädti, (Farmer
î
at al., 1981), these preparations have not been used to develop a suitable
RIA .
Ï _;
Recently, a highly purified preparation of GH has been obtained from
pituitaries of the common carp (A. Cook a£ al., 1983). Carp GH has many bio—
chemical and immunological similarities to other vertebrate GH preparations,
ï
including a similar molecular weight (22,500 Daltons), amino acid composition
and behavior on various chromatographic systems (A° Cook ag al., 1983)» The
biological activity of this carp GH preparation was assessed by determining
its
growth—promoting activity in a near—homologous bioassay using intact
goldfish, Carassius auratus (A° Cook a; al., 1983). In the goldfish, intraperitoneal injection of carp GH at a dose of 1.0 ug/g body weight of fish
resulted in a 3.2 fold increase in growth rate (based on changes in body
weight), compared to pretreatment growth rates and to intact vehicle—injected
goldfish, after only two injections of carp GH at three day intervals- Bovine
GH also caused a similar increase in growth rate, although no clear dose
response was evident
(A- COOk ʣ al., 1983). Results from a preliminary
experiment also show that twice—weekly intraperitoneal injections of a
rabbit anti—carp GH antiserum (50 ul per injection) caused a significant
decrease in growth rate in goldfish after one week of treatment (Table 1);
however, in the second week of treatment, growth rates recovered to a level
similar to control fish injected twice—weekly with normal rabbit serum (50 l
per
injection). Although preliminary, this suggests that endogenous circulat‘
ing GH in the goldfish was neutralized by passive immunization With the
rabbit anti—carp GH antiserum. These results in goldfish indicate that the
carp GH Pr6paration possesses significant biological activity in at least a
one
closely—related teleost species.
The carp GH has been used to develop and validate a RIA suitable for
measuring circulating levels of GH in the goldfish (A. Cook Ê£ êl°: 1983). In
T.A. Marchanî et ai…
GENERAL
INTRODUCTION
In vertebrates, pituitary growth hormone (GH) is the primary regulator
of
somatic growth (Donaldson a£ al., 1979). In teleost fishes, hypophysectomy
has
been shown to result in a large reduction or a cessation of linear growth
Ÿ
in several species, including killifish, Fundulus heteroclitus,
(Pickford,
1957), guppy, Poecilia latipinna, (Ball and Hawkins, 1976), rainbow trout,
Salmo gairdnerii, (Donaldson and McBride, 1967), and catfish, la£ala£aa
melas, (Kayes, 1977a; 1977b), whereas replacement therapy with a purified
preparation of GH results in a resumption of growth in hypopbysectomized
'
animals
(Pickford, 1957; Kayes, 1977a, 1977b). In addition, the exogenous
?
administration of GH preparations to intact fish results in an augmentation
Ï
of growth, as demonstrated in several salmonid species (Komourdjian al al.,
1976; Clarke ag al., 1977; Donaldson al al., 1979), tilapia, Oreochromis
Ï
(Tilapia) mossambicus, (Clarke a£ al., 1977), and common carp, Cyprinus
…
carpio, (Ade1man, 1977). The possible application of various GH preparations
and growth—promoting substances in piscine aquaculture has also been studied
‘
(Donaldson ag al., 1979).
:
Alth0ugh studies in teleost species have established that the pituitary
gland and GH are essential for normal somatic growth, very little is known
,
about the physiology of circulating GH or the neural regulation of GH secre—
Ï
tion in teleosts, in spite of its potential uses in aquaculture° One of the
factors
contributing to this paucity of information has been the lack of a
highly purified preparation of teleost GH suitable for the development and
validation of a specific radioimmunoassay (RIA) for the measurement of circu—
lating levels of GH. Although GH preparations have been obtained from several
teleost species, including tilapia (Farmer ag al., 1976), chum sa1mon, Oncor—
hynchus ka£a, (Wagner ag al., 1983; Kawauchi a£ al., 1985), coho salmon, Q;
kisutch, (Steiny a£ al., 1984), and sturgeon, Acipenser güldenstädti, (Farmer
î
at al., 1981), these preparations have not been used to develop a suitable
RIA .
Ï _;
Recently, a highly purified preparation of GH has been obtained from
pituitaries of the common carp (A. Cook a£ al., 1983). Carp GH has many bio—
chemical and immunological similarities to other vertebrate GH preparations,
ï
including a similar molecular weight (22,500 Daltons), amino acid composition
and behavior on various chromatographic systems (A° Cook ag al., 1983)» The
biological activity of this carp GH preparation was assessed by determining
its
growth—promoting activity in a near—homologous bioassay using intact
goldfish, Carassius auratus (A° Cook a; al., 1983). In the goldfish, intraperitoneal injection of carp GH at a dose of 1.0 ug/g body weight of fish
resulted in a 3.2 fold increase in growth rate (based on changes in body
weight), compared to pretreatment growth rates and to intact vehicle—injected
goldfish, after only two injections of carp GH at three day intervals- Bovine
GH also caused a similar increase in growth rate, although no clear dose
response was evident
(A- COOk ʣ al., 1983). Results from a preliminary
experiment also show that twice—weekly intraperitoneal injections of a
rabbit anti—carp GH antiserum (50 ul per injection) caused a significant
decrease in growth rate in goldfish after one week of treatment (Table 1);
however, in the second week of treatment, growth rates recovered to a level
similar to control fish injected twice—weekly with normal rabbit serum (50 l
per
injection). Although preliminary, this suggests that endogenous circulat‘
ing GH in the goldfish was neutralized by passive immunization With the
rabbit anti—carp GH antiserum. These results in goldfish indicate that the
carp GH Pr6paration possesses significant biological activity in at least a
one
closely—related teleost species.
The carp GH has been used to develop and validate a RIA suitable for
measuring circulating levels of GH in the goldfish (A. Cook Ê£ êl°: 1983). In