Dietary arginine degradation is a major pathway in ureagenesis in juvenile turbot (Psetta maxima)

M.F. Gouillou-Coustans, V. Fournier, R. Métailler, C. Vachot, E. Desbruyères, C. Huelvan, J. Moriceau, H. Le Delliou, S.J. Kaushik-2002

Comparative Biochemistry and Physiology - Part A: Molecular and Integrative Physiology, 132(2): 305-319
Abstract:

Recent studies indicate that urea excretion is responsive to protein intake and that turbot, Psetta maxima, appear to differ from other species by their urea excretion pattern and levels. This study was undertaken to evaluate the influence of dietary nitrogen and arginine on ureagenesis and excretion in turbot. Juvenile turbot (29 g) were fed semi-purified diets containing graded levels of nitrogen (0-8% dry matter) and arginine (0-3% dry matter) for 6 weeks. Growth data showed that turbot have high dietary nitrogen (123 mg/kg metabolic body weight/day) and very low dietary arginine (9.3 mg/kg metabolic body weight/day) requirements for maintenance. Requirements for unit body protein accretion were 0.31 g and 0.15 g for nitrogen and arginine respectively. Post-prandial plasma urea levels and urea excretion rates showed that urea production was significantly (P<0.05) influenced by dietary arginine levels. While hepatic arginase (EC 3.5.3.1) activity increased significantly (P<0.05) with increasing dietary arginine levels, activities of other enzymes of the ornithine urea cycle were very low. Our data strongly suggest that the ornithine urea cycle is not active in the turbot liver and that dietary arginine degradation is a major pathway of ureagenesis in turbot.

(Laboratoire de Nutrition des Poissons, Unité mixte INRA-IFREMER, Station d'Hydrobiologie, INRA, B.P 3, 64310 St Pée sur Nivelle, France, Tel.: +33-5-59-51-59-90; fax: +33-5-59-54-51-52, e-mail of S.J. Kaushik : kaushik@st-pee.inra.fr)

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