Ca(2+) mobilization evoked by chloroform in Madin-Darby canine kidney cells.

The effect of chloroform on Ca(2+) mobilization in Madin-Darby canine kidney cells was examined by using Fura-2 as a Ca(2+) probe. Chloroform (24-248 mM) concentration dependently increased intracellular Ca(2+) concentration (Ca(2+)). Ca(2+) removal inhibited the Ca(2+) signals evoked by 93 to 248 mM chloroform by reducing both the initial rise and the sustained phase. In Ca(2+)-free medium, pretreatment with 93 mM chloroform abolished the Ca(2+) release induced by 1 microM thapsigargin, an endoplasmic reticulum Ca(2+) pump inhibitor, and partially reduced the Ca(2+) release induced by 2 microM carbonylcyanide m-chlorophenylhydrazone, a mitochondrial uncoupler. Pretreatment with carbonylcyanide m-chlorophenylhydrazone and thapsigargin to deplete the Ca(2+) stores in mitochondria and the endoplasmic reticulum, respectively, only partially inhibited chloroform-induced Ca(2+) release. This suggests that chloroform released Ca(2+) from multiple internal pools. The addition of 3 mM Ca(2+) increased Ca(2+) after pretreatment with 93 mM chloroform in Ca(2+)-free medium. La(3+) (1 mM) partially inhibited the Ca(2+) increase induced by 93 mM chloroform. Chloroform (93 mM)-induced Ca(2+) release was not altered when the formation of inositol-1,4,5-trisphosphate was abolished by U73122 (2 microM), a phospholipase C inhibitor, but was inhibited by 90% by inhibition of phospholipase A(2) with 40 microM aristolochic acid. Collectively, we found that 93 mM chloroform increased Ca(2+) in Madin-Darby canine kidney cells by releasing Ca(2+) from multiple stores in a manner independent of the formation of inositol-1,4,5-trisphosphate, followed by Ca(2+) entry from external medium. Other solvents, such as ethanol, methanol, and DMSO, did not affect the resting Ca(2+) at a concentration of 248 mM.