EFFECTS OF GROWTH-HORMONE AND INSULIN-LIKE GROWTH-FACTOR-I ON SALINITY TOLERANCE AND GILL NA-ATPASE IN ATLANTIC SALMON (SALMO-SALAR) - INTERACTION WITH CORTISOL(, K+)
Sd. Mccormick, EFFECTS OF GROWTH-HORMONE AND INSULIN-LIKE GROWTH-FACTOR-I ON SALINITY TOLERANCE AND GILL NA-ATPASE IN ATLANTIC SALMON (SALMO-SALAR) - INTERACTION WITH CORTISOL(, K+), General and comparative endocrinology, 101(1), 1996, pp. 3-11
The potential roles of growth hormone (GH) and insulin-like growth fac
tor I (IGF-I) in seawater (SW) acclimation of juvenile Atlantic salmon
(Salmo salar) were examined. Compared to controls, fish in 12 ppt sea
water given one or three injections (2-6 days) of GH (ovine, 0.2 mu g
. g(-1)) or IGF-I (recombinant bovine, 0.05-0.2 mu g . g(-1)) had sign
ificantly greater salinity tolerance as judged by lower plasma sodium,
osmolality, and muscle moisture content following transfer to 34 ppt.
Single injections of GH and IGF-I in fish in fresh water failed to im
prove salinity tolerance following transfer to 25 ppt SW. Treatment of
fish in 12 ppt with GH or IGF-I for 2-6 days did not increase gill Na
+, K+-ATPase activity, but treatment with GH prevented decreases in gi
ll Na+, K+-ATPase activity that occurred in controls following transfe
r to 34 ppt seawater. Fish in fresh water administered GH by implants
(5.0 mu g . g(-1)) or osmotic minipumps (0.5 mu g . g(-1)day(-1)) for
7-14 days had greater gill Na+, K+-ATPase activity and salinity tolera
nce than controls. IGF-I administered by implants (0.5-1.0 mu g . g(-1
)) or osmotic minipumps (0.1 mu g . g(-1)day(-1)) for 4-14 days did no
t increase salinity tolerance or gill Na+, K+-ATPase activity. Cortiso
l implants (50 mu g . g(-1)) also increased gill Na+, K+-ATPase activi
ty and salinity tolerance after 14 days, and in combination with GH ha
d a synergistic effect. Although IGF-I and cortisol implants had no si
gnificant effect after 7 days, in combination they significantly incre
ased gill Na+, K+-ATPase activity. The results indicate that GH and co
rtisol can increase salinity tolerance and gill Na+, K+-ATPase activit
y of Atlantic salmon and together act in synergy. Although IGF-I can i
ncrease salinity tolerance in short-term treatments (2-6 days) in 12 p
pt, it is less effective than GH in increasing salinity tolerance and
gill Na+, K+-ATPase activity in long-term treatments (7-14- days) and
in interacting with cortisol. (C) 1996 Academic Press, Inc.