Endogenous Alanine, Glutamate, Aspartate, and Glutamine in the Perfused Guinea-Pig Heart: Effect of Substrates and Cardioactive Agents
- 1 January 1973
- journal article
- Published by Canadian Science Publishing in Canadian Journal of Biochemistry
- Vol. 51 (1) , 11-20
- https://doi.org/10.1139/o73-003
Abstract
The isolated, nonworking guinea-pig heart was perfused with 14C-labelled glucose, pyruvate, and acetate. Labelled and total alanine, glutamate, aspartate, and glutamine were measured. The alanine content of the heart varied directly with the medium pyruvate concentration. The sum of the concentrations of glutamate and aspartate varied inversely with the alanine concentration. The sum of alanine, glutamate, aspartate, and glutamine in the heart was constant under most perfusion conditions, but loss into the medium increased in the presence of ouabain, low Ca2+ concentration, or malonate. The sum of the total amino acids from the heart and medium remained constant under all conditions except in the presence of malonate, when it was decreased.Labelling of amino acids from 14C-labelled substrates indicated that alanine, glutamate, and aspartate exchanged readily with their α-oxo acids. However, only 30% of the glutamine exchanged with glutamate during 1 h; this proportion varied little with perfusion conditions or the metabolic flux. The results indicate that in a closed system, most of the changes in the concentrations of amino acids are brought about by transamination.Keywords
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