A combined stress hormone infusion decreases in vivo protein synthesis in human T lymphocytes in healthy volunteers

In vivo protein synthesis decreases in mononuclear cells following a combin ed stress hormone infusion given to healthy volunteers as a human trauma mo del. Here, the purpose was to further investigate this finding and to measu re in vivo protein synthesis in isolated T lymphocytes. Furthermore, the ef fects of stress hormones on the lymphocyte subpopulations and mononuclear c ells, characterized by flow cytometry and phytohemagglutinin (PHA)-induced and unstimulated proliferative responses in vitro, were elucidated. Healthy volunteers (n = 16) were randomized into 2 groups to receive either a stre ss hormone or a saline infusion for 6 hours. In vivo protein synthesis was studied before and after the treatment by measuring the incorporation of st able isotopically-labeled phenylalanine into lymphocyte and mononuclear cel l proteins. Protein synthesis decreased after stress hormone infusion in bo th tell populations: in T lymphocytes from 13.0% +/- 0.7%/d (mean +/- SID) to 8.6% +/- 2.1%/d (P < .01) and in mononuclear cells from 13.3% +/- 1.2%/d to 6.3 +/- 2.0%/d (P < .001). No change in proliferative responsiveness in vitro was observed. The stress hormone infusion produced a decrease in the percentage of T helper CD3/CD4 from 41% to 18% (P < .001), T cytotoxic CD3 /CD8 from 27% to 15% (P < .001), as well as total T CD3 cells from 69% to 3 5% (P < .001). There was an increase in the percentage of natural killer (N K) cells CD16/CD56 from 17% to 55% (P < .001). Determination of phenotypes expressed on activated T lymphocytes showed that CD3/HLA-DR Was unchanged a nd CD3/CD25 decreased from 14% to 7% (P < .01) in the stress hormone group. The study showed that the decrease of in vivo protein synthesis was 34% in T lymphocytes as compared with 53% in mononuclear cells, when determined i mmediately after a 6-hour stress hormone infusion. This change was associat ed with a pronounced decrease in all lymphocyte subpopulations, except for the NK cells, which increased substantially. Copyright (C) 2001 by W.B. Sau nders Company.