1. The stimulation and depression of peripheral blood lymphocytes has previously been studied in vitro, showing an immune depression postoperatively; however, it is difficult to interpret these in vitro findings. Therefore, an in vivo technique has been established for determination of the fractional protein synthesis rate, as an index of metabolic activity in human peripheral blood lymphocytes, by using a stable isotope technique.
2. The rate of protein synthesis was calculated from the increase in enrichment of l-[2H5]phenylalanine in protein of a mixed population of mononuclear leucocytes, isolated by density gradient, after an intravenous flooding dose of l-[2H5]phenylalanine. A linear time course of isotopic incorporation into the cells was demonstrated.
3. The fractional rate of protein synthesis of a mixed population of mononuclear leucocytes was studied in relation to surgical interventions and to potential modifiers of the response. The fractional synthesis rate increased 24 h after open and laparoscopic cholecystectomy (49 ± 19% and 40 ± 14% respectively, P > 0.02), irrespective of postoperative total parenteral nutrition or preoperative glucose infusion. In contrast to surgery, insulin did not stimulate protein synthesis in peripheral mononuclear leucocytes.