THE AMINO ACID REQUIREMENTS OF A PERMANENT STRAIN OF ALTERED UTERINE FIBROBLASTS (U12-705)

Abstract

A permanent line of altered human fibroblasts, strain U12-705, was found to require arginine, cystine, glutamine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, tryptophan, tyrosine, and valine for growth in a defined medium supplemented with 2.5% (v/v) dialyzed chick embryo extract and 5% dialyzed horse serum. In the absence of any of the essential amino acids the cells not only fail to proliferate but undergo degenerative changes which increased with time. The omission of alanine, aspartic acid, glutamic acid, glycine, hydroxyproline, and proline either separately or collectively does not alter the rate of growth or result in changes in the appearance of the cells. Cysteine and glutathione are equally as effective as cystine in promoting the growth of U12-705. None of the D-enantiomorphs of the essential amino acids will effectively replace the corresponding L-isomer. Single D-amino acids are not inhibitory when added to the medium in 5 times the concentration of the L-amino acid. The minimum concentrations of essential amino acids which permit optimal proliferation under the conditions employed range from 0.005 to 0.5 mM. Essential amino acids with the exception of glutamine, isoleucine, leucine, threonine, and valine are toxic for U12-705 when employed at a concentration of 5 mM. Toxic manifestations vary with the amino acid and range from cytologic changes in the cells without a significant decrease in the growth rate to complete inhibition of growth and extensive cellular degeneration.