Growth, osmoregulation and endocrine changes in wild Atlantic salmon smolts and post-smolts during marine migration

• We have examined physiological parameters associated with seawater adaptability, growth and energetics, as well as major endocrine regulators of these processes in wild migrating Atlantic salmon smolts and post-smolts from the river through the fjord, coastal areas and the open ocean. Muscle RNA/DNA ratio suggests that growth rate increases soon after entry into seawater and continues to increase after the post-smolts reach the offshore banks and the feeding grounds in the Norwegian Sea. Post-smolts prioritize rapid growth and protein deposition in spring and summer, and their energy intake during this period is so high that deposition of energy is possible in addition to muscle growth. An increase in thyroxine (T-4) and triiodothyronine (T-3) levels was observed, suggesting a major activation of hepatic conversion of T-4 to T-3 in post-smolts in seawater, probably related to the high metabolic activity and rapid growth and development of the post-smolts. Decreased plasma growth hormone (GH) levels were observed from the river through the fjord, with levels around 2 ng ml(-1) in rapidly growing post-smolts, concurrent with an increase in circulating insulin-like growth factor I (IGF-I). An increase in pituitary GH expression levels and hepatic GH receptor (GH-R) and local IGF-I mRNA levels suggest a physiological basis for the changes in circulating GH and IGF-I levels. Receptor expression in brain and pituitary suggests that both hormones are actively involved in the growth and differentiation of these tissues during the critical early marine phase. Gill Na+, K+-ATPase (NKA) activity increased to post-smolt levels above 20 mu mol ADP mg prot.(divided by 1) h(divided by 1), probably representing long-term NKA activity levels of Atlantic salmon in seawater. Concurrent with the changes in NKA activity the expression of the NKA alpha 1b isoform remained high in post-smolts, while the expression of the NKA alpha 1a decreased from smolts to post-smolts. Both cystic fibrosis transmembrane conductance regulator (CFTR) I and II showed a reduction in mRNA levels from smolts to post-smolts, and remained stable at low expression levels in seawater. (c) 2011 Elsevier B.V. All rights reserved.

Ämnesord

NATURVETENSKAP  -- Biologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences (hsv//eng)

Nyckelord

Energetics

Growth hormone

IGF-I

Thyroid hormones

Na plus

K plus -ATPase

IGF-I receptor

transmembrane conductance regulator

alpha-subunit isoforms

salar l.

smolts

coho salmon

factor-i

na

k

2cl(-) cotransporter

different

temperatures

seawater tolerance

northeast atlantic

thyroid-hormones

cormick sd

1989

fish physiology and biochemistry

v6

p243

keyasu k

1990

american journal of physiology

v259

pc619

cormick sd

1990

general and comparative endocrinology

v78

p224

omczynski p

1993

biotechniques

v15

p532

cormick sd

1993

canadian journal of fisheries and aquatic sciences

v50

p656

Publikations- och innehållstyp

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