Lindane differently modulates intracellular calcium levels in two populations of rainbow trout (Oncorhynchus mykiss) immune cells:: head kidney phagocytes and peripheral blood leucocytes

We studied the in vitro effects of high concentrations of the insecticide lindane (from 2.5 to 100 mu M) on intracellular calcium levels ([Ca2+](i)) in rainbow trout head kidney phagocytes and peripheral blood leucocytes (PBLs). [Ca2+](i) was measured during 6 min by spectrofluorimetry using Indo-1/AM as fluorescent probe. Lindane, from 5 to 100 mu M, increased [Ca2+](i) in PBLs and from 25 mu M in phagocytes. In Ca2+-free medium, only 50 and 100 mu M lindane increased significantly [Ca2+](i) in PBLs and only 100 mu M lindane in phagocytes. However, lindane at 5 and 10 mu M, induced a decrease in [Ca2+](i) in phagocytes suspended in Ca2+-free medium. Lindane needed extracellular calcium to rise [Ca2+](i) in phagocytes but not in PBLs. Lindane effects on endoplasmic reticulum (ER) calcium store tvas examined. In spite of mobilisation by lindane of ER calcium store in phagocytes, it had an opposite effect in PBLs. The composition of the two cell population can explain the differences in calcium modulation observed. [Ca2+](i) is an extremely important signal transduction element in physiology and modulation of [Ca2+](i) by lindane can be responsible for modulations of immune cell functions. Moreover, sustained rises in [Ca2+](i) as observed in our study may be associated with cell death and explained partially the cytotoxicity of this organochlorine insecticide on fish immune cells. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.