The Significance of Amino-Acids for the Growth in vitro of Human Fibroblasts: II. Growth in Media Containing Various Amounts of Glycine

Abstract

In a previous paper (5) it was shown that fibroblasts of the adult human thyroid gland may be grown for a considerable time in a culture medium composed of equal parts of beef plasma, calcium Ringer solution, feeding solution, and a 0.28 molar glycine solution. This medium contains 525 mg. of glycine per 100 c.c. No cellular activity, however, either in the form of cell emigration or cellular outgrowth, occurred in a medium with the same amount of this amino-acid but lacking the components of the feeding solution. Under these circumstances the glycine evidently was detrimental to the tissue since, after placing the latter in a suitable medium, no growth could be obtained. On the basis of this and other observations, the following theory was advanced to explain the wholly different behavior of fibroblasts in the two media under consideration. The toxic or beneficial influence of amino-acids is not primarily dependent on the concentration, but mainly on the chemical composition of the medium of which they form a part. When the medium contains only amino-acids, or contains them in relative superabundance, the cells will adsorb them to such an extent that they will interfere with the normal life processes. The simultaneous presence of the various groups of protein decomposition products will prevent a too exclusive adsorption of the amino-acids. In the first instance they will exert a toxic influence; in the second they may be innocuous or even beneficial to the cells. The fact that trypsin subcultures show a good growth activity in a medium which inhibits completely the growth of fresh thyroid tissue is easily understood when it is realized that during the trypsin treatment the cells have ample opportunity to adsorb various protein decomposition products and, therefore, to protect themselves from a harmful action of the glycine.