The Amide Class Herbicide 3,4-Dichloropropionanilide (DCPA) Alters the Mobility of Hydrocarbon Chains in T-Lymphocyte but not Macrophage Membranes

Abstract

Previous studies in our laboratory have demonstrated that the lipophilic herbicide 3,4-dicholoropropionanilide (DCPA) adversely affects cytokine production by activated macrophages and T lymphocytes. The purpose of this study was to test the hypothesis that DCPA alters the mobility of plasma membrane lipid hydrocarbon chains, which interferes with normal T-lymphocyte activation and macrophage function. Electron spin reasonance (ESR) spectroscopy of stearic acid spin labels incorporated into each cell type was used to test the effects of DCPA on lipid hydrocarbon chain mobility in the absence and presence of specific agents that activate each cell type. The results indicated that DCPA treatment had no significant effect on hydrocarbon chain mobility in either cell type per se. However, for T lymphocytes, but not macrophages, DCPA treatment increased a small population of lipid molecules that exhibited reduced hydrocarbon chain mobility near the bilayer hydrocarbon core following cell stimulation. In contrast, there were no significant effects of DCPA on hydrocarbon chain mobility near the head group region of the bilayer for either cell type. The identity of this subpopulation of lipids and its motional properties could not be elucidated from these studies. Nevertheless, data show that DCPA alters the distribution of lipids in distinct motional environments in the membrane of activated T lymphocytes.