title: Histamine induces oscillations of mitochondrial free Ca2+ concentration in single cultured rat brain astrocytes.
abstract: 1. The free Ca2+ concentration of mitochondria ([Ca2+]m) in cultured rat brain astrocytes was measured with a fluorescent Ca2+ indicator, rhod-2, and laser confocal microscopy. 2. Confocal images revealed a rhod-2 distribution that matched mitochondrial localization. 3. Using a Ca2+ ionophore, ionomycin, to clamp the [Ca2+]m from 0 to 100 microM in order to obtain the minimal and maximal fluorescence of rhod-2 in situ, a 3.5 +/- 0.4-fold increase in fluorescence intensity was observed, suggesting that the fluorescence of intramitochondrial rhod-2 was responding in a Ca(2+)-sensitive manner, thereby allowing measurements of [Ca2+]m in single astrocytes. 4. Exposure of fura-2-loaded astrocytes to 100 microM histamine produced a rapid and transient increase in cytosolic Ca2+ concentration ([Ca2+]c) that lasted for several tens of seconds. The spike in [Ca2+]c was frequently followed by variable numbers of repetitive oscillations of Ca2+, which appeared to dampen in amplitude with time. 5. This pattern of histamine-induced [Ca2+]c oscillations was also observed in rhod-2-loaded cells suggesting that [Ca2+]m fluctuated with a similar frequency. 6. The oscillations of [Ca2+]m, but not of [Ca2+]c, were abolished by a proton ionophore, carbonyl cyanide m-chlorophenyl-hydrazone (CCCP), and by Ruthenium Red, a mitochondrial Ca(2+)-uniporter inhibitor. 7. These results suggest that the mitochondrial Ca2+ transport systems in cultured rat brain astrocytes are able to relay receptor-mediated [Ca2+]m oscillations into mitochondria.
authors.affiliation: Department of Pharmacology and Physiology, School of Medicine and Dentistry, University of Rochester, NY 14642-8711, USA.
authors.forename: M J
authors.initials: MJ
authors.lastname: Jou
authors.forename: T I
authors.initials: TI
authors.lastname: Peng
authors.forename: S S
authors.initials: SS
authors.lastname: Sheu
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000166:cytology* / Q000648:ultrastructure; D002118:Calcium / Q000378:metabolism*; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D002460:Cell Line / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D004396:Coloring Agents / Q000494:pharmacology; D006632:Histamine / Q000494:pharmacology*; D007091:Image Processing, Computer-Assisted; D007476:Ionophores / Q000494:pharmacology; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D012430:Ruthenium Red / Q000494:pharmacology
chemical_list: D004396:Coloring Agents; D007476:Ionophores; D012430:Ruthenium Red; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D006632:Histamine; D002118:Calcium