Cadmium is acutely toxic for murine hepatocytes: effects on intracellular free Ca(2+) homeostasis.
We studied cadmium toxicity in murine hepatocytes in vitro. Cadmium effects on intracellular free Ca(2+) concentration ([Ca(2+)](i)) were assayed, using a laser scanning confocal microscope with a fluorescent probe, Fluo-3/AM. The results showed that administration of cadmium chloride (CdCl(2), 5, 10, 25 microM) resulted in a dose-dependent decrease of hepatocyte viability and an elevated aspartate aminotransferase (AST) activity in the culture medium (p<0.05 for 25 microM CdCl(2) vs. control). Significant increases of lactate dehydrogenase (LDH) activities in 10 and 25 microM CdC1(2)-exposed groups were observed (p<0.05 and p<0.01, respectively). A greatly decreased albumin content and a more malondialdehyde (MDA) formation also occurred after CdC1(2) treatment. The Ca(2+) concentrations in the culture medium of CdCl(2)-exposed hepatocytes were significantly decreased, while [Ca(2+)](i) appeared to be significantly elevated (p<0.05 or p<0.01 vs. control). We found that in Ca(2+)-containing hydroxyethyl piperazine ethanesulfonic acid-buffered salt solution (HBSS) only, CdCl(2) elicited [Ca(2+)](i) increases, which comprised an initially slow ascent and a strong elevated phase. However, in Ca(2+)-containing HBSS with addition of 2-aminoethoxydiphenyl borane (2-APB), CdCl(2) caused a mild [Ca(2+)](i) elevation in the absence of an initial rise phase. Removal of extracellular Ca(2+) showed that CdCl(2) induced an initially slow [Ca(2+)](i) rise alone without being followed by a markedly elevated phase, but in a Ca(2+)-free HBSS with addition of 2-APB, CdCl(2) failed to elicit the [Ca(2+)](i) elevation. These results suggest that abnormal Ca(2+) homeostasis due to cadmium may be an important mechanism of the development of the toxic effect in murine hepatocytes. [Ca(2+)](i) elevation in acutely cadmium-exposed hepatocytes is closely related to the extracellular Ca(2+) entry and an excessive release of Ca(2+) from intracellular stores.
College of Life Sciences, Nanjing Normal University, Nanjing, Jiangsu, China.
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Wang
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Chen
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Xia
D000418:Albumins / Q000378:metabolism; D000814:Aniline Compounds; D000818:Animals; D000831:Animals, Newborn; D001219:Aspartate Aminotransferases / Q000378:metabolism; D001896:Boron Compounds / Q000494:pharmacology; D019256:Cadmium Chloride / Q000633:toxicity*; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004785:Environmental Pollutants / Q000633:toxicity*; D005456:Fluorescent Dyes; D022781:Hepatocytes / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D006706:Homeostasis / Q000187:drug effects; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000037:antagonists & inhibitors / Q000378:metabolism; D042541:Intracellular Space / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008315:Malondialdehyde / Q000378:metabolism; D051379:Mice; D008813:Mice, Inbred ICR; D018613:Microscopy, Confocal; D013997:Time Factors; D014966:Xanthenes
D000418:Albumins; D000814:Aniline Compounds; D001896:Boron Compounds; D004785:Environmental Pollutants; D005456:Fluorescent Dyes; D053496:Inositol 1,4,5-Trisphosphate Receptors; D014966:Xanthenes; C059715:Fluo-3; D008315:Malondialdehyde; C109986:2-aminoethoxydiphenyl borate; D007770:L-Lactate Dehydrogenase; D001219:Aspartate Aminotransferases; D019256:Cadmium Chloride; D002118:Calcium