Lindane (γ-hexachlorocyclohexane) induces internal Ca²⁺ release and capacitative Ca²⁺ entry in Madin-Darby canine kidney cells

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).