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15N enrichment of casein amino acids in the milk from goats given a single intravenous dose of l-[15N]leucine

Published online by Cambridge University Press:  01 May 1999

JOAQUIN RUBERT-ALEMÁN
Affiliation:
INRA Ecole Nationale Supérieure d'Agronomie et des Industries Alimentaires, Laboratoire de Sciences Animales, 2 avenue de la Forêt de Haye, BP 172, F-54505 Vandœuvre-lès-Nancy Cedex, France
GUIDO RYCHEN
Affiliation:
INRA Ecole Nationale Supérieure d'Agronomie et des Industries Alimentaires, Laboratoire de Sciences Animales, 2 avenue de la Forêt de Haye, BP 172, F-54505 Vandœuvre-lès-Nancy Cedex, France
FLORENCE CASSERON
Affiliation:
Laboratoire d'Analyse Isotopique et Électrochimique des Métabolismes, UPRES-A 6006, Université de Nantes, 2 rue de la Houssinière, BP 92208, F-44322 Nantes Cedex 03, France
Formerly Laboratoire de RMN et Réactivité Chimique, URA-CNS 472, Université de Nantes, 2 rue de la Houssinière, BP 92208, F-44322 Nantes Cedex 03, France.
FRANCOIS LAURENT
Affiliation:
INRA Ecole Nationale Supérieure d'Agronomie et des Industries Alimentaires, Laboratoire de Sciences Animales, 2 avenue de la Forêt de Haye, BP 172, F-54505 Vandœuvre-lès-Nancy Cedex, France
GERARD JEAN MARTIN
Affiliation:
Laboratoire d'Analyse Isotopique et Électrochimique des Métabolismes, UPRES-A 6006, Université de Nantes, 2 rue de la Houssinière, BP 92208, F-44322 Nantes Cedex 03, France
Formerly Laboratoire de RMN et Réactivité Chimique, URA-CNS 472, Université de Nantes, 2 rue de la Houssinière, BP 92208, F-44322 Nantes Cedex 03, France.

Abstract

Branched-chain amino acids (AA) are mostly metabolized in the splanchnic area, but some are metabolized within the mammary gland and thus could contribute to the synthesis of non-essential AA (Wohlt et al. 1977). The extraction rate of leucine from plasma by the mammary gland is particularly high (64% in the goat; Roets et al. 1983), in excess of that used for the synthesis of milk proteins (Davis & Mepham, 1976; Wohlt et al. 1977; Roets et al. 1983). Thus, although mammary leucine is mainly used for milk protein, it also provides amino nitrogen and carbon sources for the synthesis of non-essential AA.

To our knowledge, no information is available on the transfer and distribution of plasma leucine amino nitrogen to milk protein AA. Using the technique for chromatographic fractionation of AA recently developed by Casseron et al. (1997), we studied the specific 15N enrichment of casein (CN) AA in the goat given a single intravenous injection of [15N]leucine.

Type
SHORT COMMUNICATION
Copyright
Proprietors of Journal of Dairy Research 1999

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