Lindane (γ‐Hexachlorocyclohexane) Induces Internal Ca2+ Release and Capacitative Ca2+ Entry in Madin‐Darby Canine Kidney Cells

Abstract:The effect of lindane (γ‐hexachlorocyclohexane), an organochlorine pesticide, on Ca2+ mobilization in Madin‐Darby canine kidney cells was examined by fluorimetry using fura‐2 as a Ca2+ indicator. Lindane (5–200 μM) increased [Ca2+]i concentration‐dependently. The [Ca2+]i signal comprised an immediate initial rise followed by a persistent phase. Ca2+ removal inhibited the [Ca2+]i signal by reducing both the initial rise and the sustained phase. This implies lindane‐triggered Ca2+ influx and Ca2+ release. In Ca2+‐free medium, 0.15 mM lindane increased [Ca2+]i after pretreatment with carbonylcyanide m‐chlorophenylhydrazone (CCCP; 2 μM), a mitochondrial uncoupler, and two endoplasmic reticulum Ca2+ pump inhibitors, thapsigargin and cyclopiazonic acid. Conversely, pretreatment with lindane abolished CCCP‐ and thapsigargin‐induced Ca2+ release. This suggests that 0.15 mM lindane released Ca2+ from the endoplasmic reticulum, mitochondria and other stores. La3+ (1 mM) partly inhibited 0.1 mM lindane‐induced [Ca2+]i increase, confirming that lindane induced Ca2+ influx. Addition of 3 mM Ca2+ increased [Ca2+]i after pretreatment with 0.15 mM lindane for 750 sec. in Ca2+‐free medium, which indicates lindane‐induced capacitative Ca2+ entry. Lindane (0.15 mM)‐induced Ca2+ release was not reduced by inhibiting phospholipase C with 2 μM U73122, but was inhibited by 70% by the phospholipase A2 inhibitor aristolochic acid (40 μM).