Biology Reference
In-Depth Information
6.3.2.2.2 Metabolism
Treatment with trout recombinant GH in FW resulted in a signifi cant
increase in gill (Na+K+)ATPase activity and in standard metabolism, and
after direct transfer from FW to SW, attenuated the decrease in O2 affi nity of
hemoglobin foreseeable from the metabolic acidosis (Seddiki et al., 1995).
Preparations of GH from mammals and fi sh appear to be growth-
promoting in a number of different teleosts (Donaldson et al., 1979). Free
fatty acids are mobilized by GH in coho (Markert et al., 1977) and sockeye
(Leatherland et al., 1974; McKeown et al., 1975) salmon. GH stimulated lipid
mobilization from coho salmon parr with depletion of liver total lipids,
increased lipolytic enzyme (triacylglycerol lipase) activity, while it had no
effect in smolts (Sheridan, 1986). GH may also be diabetogenic (rainbow
trout: Enomoto, 1964; sockeye salmon: McKeown et al., 1975). Injections of
GH in juvenile coho salmon resulted in increases in plasma glucose levels
but did not change plasma amino acid nitrogen levels (Sweeting et al., 1985).
This hyperglycaemic effect of GH appeared to be dependent on the degree of
smoltifi cation of the coho juveniles (Sweeting et al., 1985). GH also appears
to have a protein anabolic effect (
Salmo irideus
: Enomoto, 1964).
6.3.2.2.3 Osmoregulation
6.3.2.2.3.1 GH
In salmonids, many studies demonstrated that osmoregulation and SW
adaptability is not regulated by thyroid hormones (see section 2.1.2.5.)
but by GH. The effect of GH treatment on smoltifi cation and seawater
adaptability is well known (Smith, 1956; Komourdjian et al., 1976b; Clarke
et al., 1977; Miwa and Inui, 1985; Bolton et al., 1987; Collie et al., 1989). The
treatment with GH has been shown to have a positive infl uence on growth,
smoltifi cation and SW adaptability in juvenile Atlantic (Boeuf et al., 1990,
1994), coho salmon (Richman and Zaugg, 1987), in rainbow trout (Madsen,
1990b; Seddiki et al., 1995) and sea trout (Madsen, 1990c).
Treatment with GH (ovine or recombinant trout) of Atlantic salmon
presmolts prior to smoltifi cation (November, December and February)
increased gill Na+, K+-ATPase activity and salinity tolerance, while
treatment during April, May or June induced no difference compared to
controls (Boeuf et al., 1994). Injections of juvenile coho salmon with bovine
GH signifi cantly increased corticosteroid receptor (CR) concentration in the
gills, which may increase responsiveness of the gills to cortisol (Shrimpton
et al., 1995). In addition, Shrimpton and McCormick (1998a) showed, in
Atlantic salmon, that injection of ovine GH signifi cantly increased gill
