title: [ACTION OF MODULATORS OF LARGE-CONDUCTANCE Ca2+-ACTIVATED K+ CHANNELS ON RAT ASCITES HEPATOMA CELLS AND ISOLATED RAT LIVER MITOCHONDRIA TREATED BY Cd2+].
abstract: ATP-producing cell organelles, mitochondria, are the primary target for heavy metals which are major environmental pollutants and cause various pathological conditions and diseases. It has been established that the mechanism of toxic action of heavy metals, includes changes in the intracellular production of reactive oxygen species and mitochondrial dysfunction mediated by disturbances of the respiratory chain and by activation of Ca2+-dependent nonselective pore of the inner mitochondrial membrane. The role of other ion channels, in particular such selective potassium channels as Ca2+ activated large-conductance potassium channels, BK(Ca), considered to be <<protective>> for a cell, is practically not investigated. In the present work on rat ascites hepatoma AS-30D cells and isolated rat liver mitochondria we studied action of different BK(Ca) effectors in the absence and presence of Cd2+ in the assay medium, namely of two its openers, N51619 and N5004,and one blocker, paxilline. After 24 h-incubation of AS-30D cells with 10 µM of either NS 1619 or N5004, the number of apoptotic cells was found to increase compared with control. Besides, the presence of these BK(Ca) openers in the media produced an additive effect on Cd2+-induced apoptosis of AS-30D cells. The same concentration of N51619 and N5004 did not affect significantly respiration ofAS-30D cells after 3, 24 and 48 h of incubation but produced a substantial increase in intracellular production of reactive oxygen species after 3 h of the treatment. In experiments on isolated rat liver mitochondria NS1619 and N5004, added at the same concentration to the KCI-containing medium, had no effect on the respiratory rate at state 3 by Chance and on the maximally uncoupled respiration rate (both in the presence and absence of Cd2+); at the same time they induced a weak uncoupling action by accelerating the basal respiration and the resting state respiration (at state 4 by Chance) as well as they enlarged the high-amplitude mitochondrial swelling induced by Cd2+ in this medium. It was shown that paxilline, at concentration of 1 µM, decreased the mortality of AS-30D cells after 3, 24 and 48 h of incubation in the presence of Cd2+ and enhanced intracellular production of reactive oxygen species in control cells after 3 and 24 h of incubation. At concentration producing a long-term protective effeet, paxilline did not influence the respiration of AS-30D cells and isolated rat liver mitochondria (both in the presence and absence of Cd2+) and did not decrease mitochondrial swelling observed in the presence of Cd2+ and the BK(Ca) activators. Possible molecular mechanisms of action of the BK(Ca) modulators are discussed.
authors.forename: E L
authors.initials: EL
authors.lastname: Belyaeva
mesh_terms: D000818:Animals; D002104:Cadmium / Q000633:toxicity*; D045744:Cell Line, Tumor; D004579:Electron Transport / Q000187:drug effects*; D007211:Indoles / Q000494:pharmacology; D008930:Mitochondria, Liver / Q000187:drug effects* / Q000201:enzymology / Q000473:pathology; D051336:Mitochondrial Membranes / Q000187:drug effects / Q000201:enzymology; D008933:Mitochondrial Swelling / Q000187:drug effects; D009924:Organ Culture Techniques; D024681:Potassium Channels, Calcium-Activated / Q000378:metabolism*; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D007211:Indoles; D024681:Potassium Channels, Calcium-Activated; D017382:Reactive Oxygen Species; D002104:Cadmium; C048220:paxilline