Investigation of intracellular magnesium mobilization pathways I PC12 cells B simultaneous Mg-Ca fluorescent imaging.
OBJECTIVE
PC12 cells were loaded with a novel Mg indicator KMG-104 and Ca indicator fura-2, and intracellular Mg was studied in the endoplasmic reticulums (ERs), mitochondria, and Mg-ATP. Under coexistence of the two indicators, fluorescent signals of Mg and Ca can be measured separately. Mg release from the ER was investigated by photolysis of caged compounds.


RESULTS
Transient [Ca]i increase by uncaging of caged Ca or caged IP3 or bath-application of caffeine (10 mM) induced no [Mg]i increase. These results suggest that there is no mechanism for Mg release from the ER through ryanodine receptors or IP3 receptors. In order to investigate the possibility of Mg release from Mg-ATP by energy consumption, we depleted ATP by oligomycin, an inhibitor of mitochondrial ATP synthase. Treating with oligomycin (4 microM) for several minutes showed no change of [Mg]i and [Ca]i.


CONCLUSIONS
This result shows that Mg-ATP is not a Mg store. Since, when cells were treated by an uncoupler FCCP (3 microM), [Mg]i and [Ca]i increased, we concluded that mitochondria participate in maintenance of intracellular Mg stores.
Kubota
Takeshi
T
School of Fundamental Science and Technology, Keio University, Yokohama, Japan.
Shindo
Yutaka
Y
Tokuno
Kentaro
K
Komatsu
Hirokazu
H
Ogawa
Hiroto
H
Kitamura
Yoshiichiro
Y
Suzuki
Koji
K
Oka
Kotaro
K
D002118:Calcium / Q000737:chemistry / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism*; D002478:Cells, Cultured; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D005456:Fluorescent Dyes; D006801:Humans; D053496:Inositol 1,4,5-Trisphosphate Receptors; D008274:Magnesium / Q000737:chemistry / Q000378:metabolism*; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*
D015220:Calcium Channels; D005456:Fluorescent Dyes; C506926:ITPR1 protein, human; D053496:Inositol 1,4,5-Trisphosphate Receptors; D018160:Receptors, Cytoplasmic and Nuclear; D008274:Magnesium; D002118:Calcium