Abstract
Recently much attention has focused on the method whereby living cells regulate their external environment. It is generally accepted that an active metabolic process is involved. Hoffman (1) and Post (2) in reviews present adequate evidence that an active process transporting Na and K is present in the erythrocyte membrane. Keynes in a symposium (3) spoke of the same process existing in nerves and muscle. The author went on to show that ATP is considered the source of energy for these active processes. | As early as 1912 evidence was observed by Van Slyke and Meyer (4) that amino acids are accumulated by cells. Christensen (5) using ascites tumor cells demonstrated amino acid active transport and postulated pyridoxal as the active carrier. Two of the latter's symposia (6, 7) present more than sufficient evidence regarding the existence of this active process. | In view of these references, it was of interest to us to study ion, amino acid, and osmotic pressure changes that occur when cells are incubated in tissue culture media as opposed to changes that occur when they are incubated in natural media, i.e., serum.