Expression and Characterization of European Sea Bass (Dicentrarchus labrax) Somatolactin: Assessment of In Vivo Metabolic Effects

: AbstractThe complementary DNA coding for European sea bass somatolactin was expressed in the pET-3a bacteria expression vector. The recombinant somatolactin (rbSL) was purified by size exclusion chromatography, and 95% of the protein remained in the oxidized form with negligible aggregation over p...

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Bibliographic Details
Published in:Marine biotechnology (New York, N.Y.) N.Y.), 2003-01, Vol.5 (1), p.92-101
Main Authors: Vega-Rubín de Celis, S, Gómez, P, Calduch-Giner, J A, Médale, F, Pérez-Sánchez, J
Format: Article
Language:English
Subjects:
Animals
Bacteria
Bass
Bass - metabolism
Biological activity
Biological Assay
Cloning, Molecular
Dicentrarchus labrax
Fish Proteins
Gene expression
Glycoproteins - biosynthesis
Glycoproteins - metabolism
Growth Hormone - physiology
Growth hormones
Insulin
Insulin-like growth factors
Life Sciences
Marine biology
Metabolism
Molecular weight
Pituitary Hormones - biosynthesis
Pituitary Hormones - metabolism
Plasmids
Proteins
Radioimmunoassay
Recombinant Proteins - biosynthesis
somatolactin
Studies
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Summary:: AbstractThe complementary DNA coding for European sea bass somatolactin was expressed in the pET-3a bacteria expression vector. The recombinant somatolactin (rbSL) was purified by size exclusion chromatography, and 95% of the protein remained in the oxidized form with negligible aggregation over prolonged cold storage. The identity of the recombinant protein was demonstrated by Western blotting with a rabbit polyclonal antibody against gilthead sea bream somatolactin. The same antibody was utilized in a radioimmunoassay procedure, using rbSL as standard and radioiodinated tracer. Curve displacements of pituitary and plasma samples paralleled the rbSL standard, and the midrange of the assay (8 ng/ml) was low enough to measure in a consistent manner the circulating SL concentration. To assess biological activity a single dose of rbSL (0.1 µg/g of body mass) was administered to juvenile gilthead sea bream by intraperitioneal injection. In comparison with saline-treated fish, rbSL did not modify the circulating amount of insulin-like growth factor I, whereas a 50% increase was found with the same dose of recombinant trout growth hormone (rtGH). Hormone treatment did not modify nitrogen-ammonia excretion, but both rbSL and rtGH increased carbon dioxide output and oxygen uptake, which in turn decreased the respiratory quotient (CO₂ output per O₂ uptake). This pattern of gas exchange suggests the enhancement of lipid catabolism, which is consistent with the observation that both hormones were able to inhibit the hepatic activity of acetyl–coenzyme A carboxylase. These new insights provide direct evidence for the involvement of fish somatolactin in energy homeostasis, which may serve to maintain the lipolytic tonus in different physiologic states.
ISSN:1436-2228
1436-2236
DOI:10.1007/s10126-002-0053-6