Effects of hexachlorocyclohexane isomers on the mitogenic response of bovine lymphocytes

The α-, β-, γ- and δ-isomers of hexachlorocyclohexane (HCH) were evaluated as modifiers of the mitogenic response in cultured bovine lymphocytes. None of the four isomers were mitogenic alone; however, the concurrent administration of αHCH and phytohemagglutinin-P (PHA) stimulated DNA synthesis in lymphocyte cultures 2.2-fold over that obtained with PHA alone. βHCH was inactive in the test system whereas both γ- and δHCH severely inhibited the PHA response. Treatment of lymphocytes with the microsomal enzyme inhibitor SKF-525A blocked the co-mitogenic activity of αHCH without affecting the basal PHA response. The role of hexachlorocyclohexane-sensitive metabolic systems in the regulation of mitogenesis in lymphocytes is discussed.