The effects of tumour growth on circulating amino acids in the late pregnant rat.

The implantation of a rapidly-growing tumour--the AH-130 Yoshida ascites hepatoma--to late pregnant rats resulted in important changes in both the maternal and fetal amino acid concentrations. Increased concentrations of most amino acids--glycine, alanine, threonine, serine, proline, glutamate+glutamine, valine, leucine, isoleucine, phenylalanine, tyrosine and lysine--are found in the fetal circulation, the concentration of total and essential amino acids being clearly higher than in the non-tumour bearing controls. In the maternal circulation, the presence of the tumour also caused increases in the concentration of glycine, lysine, glutamate+glutamine and arginine. Conversely, tumour-bearing rats had lower concentrations of threonine, serine, aspartate+asparagine, valine, leucine, phenylalanine and histidine. These results support the described increased fetal availability of amino acids during tumour growth (Carbó, N., López-Soriano, F.J. and Argilés, J.M. (1994). In the late pregnant rat, tumour growth results in an increased availability of fetal amino acids. Biochem. J., in press) and allow us to suggest that important changes in placental amino acid transport systems must be induced by tumour burden.