Incorporation of amino acids into protein from an intracellular pool of lymphocytes.

The nature of the precursor pool for protein synthesis in porcine lymphocytes has been investigated. Intracellular free glycine was found to be used in preference to its extracellular counterpart. It is suggested that a similar preference applies for all amino acids. However, with certain amino acids such as phenylalanine, this preference is difficult to demonstrate because of a rapid exchange occurring between intracellular and extracellular pools. A small portion of the intracellular phenylalanine pool was found not to exchange rapidly but this was not important in the maintenance of protein synthesis. A different type of compartmentation of the intracellular glycine pool was apparent, but this was less well defined. During the course of these investigations it was demonstrated that the nature of the incubation medium is an important consideration for enabling correct interpretation of kinetic experiments. To maintain what appeared to be a constant rate of protein synthesis, lymphocytes had to be incubated in a comprehensive culture medium (basal Eagle's medium without serum); a declining rate of synthesis was observed if a simple buffered salts medium (Krebs-Ringer bicarbonate buffer) was used.