Free amino acid pools of rodent mammary tumors

Intracellular pools of free amino acids were compared individually in mammary tumors of Wistar Furth and Sprague-Dawley rats and C3H and DBA/2 mice. Of 11 transplantable and 7,12-dimethylbenz[a]anthracene-induced adenocarcinomas of the rat, all nonmetastasizing tumors could be distinguished from metastasizing tumors by the accumulation of high glutamine pools and significant-to-high cystathionine pools. In primary mammary tumors of C3H mice and transplanted mammary tumors of DBA/2 mice, intracellular free arginine was frequently below that of the circulating plasma level and approached that in the arginine-destroying organ, the liver. Arginine pool depletion was also noted in normal mammary tissue, particularly in the actively lactating mouse. Individual rat or mouse mammary tumors also contained high levels of taurine, beta-alanine, and gamma-aminobutyric acid, which, like cystathionine, are distinctive for or are enriched in neural tissue. None of these pool enrichments were characteristic of normal rat or mouse mammary tissue. Free hydroxyproline was low in primary induced rat mammary tumors and higher in transplanted mammary tumors and in normal lactating mammary glands, particularly in the mouse. In contrast, the hydroxyproline residues of collagen, taken as an index of mesenchymal cell contribution, were very low in all tumors.