title: Rhythmic fluctuations in the concentration of intracellular Mg2+ in association with spontaneous rhythmic contraction in cultured cardiac myocytes.
abstract: Magnesium ions (Mg(2+)) play a fundamental role in cellular function, but the cellular dynamic changes of intracellular Mg(2+) remain poorly delineated. The present study aims to clarify whether the concentration of intracellular Mg(2+) possibly changes cyclically in association with rhythmic contraction and intracellular Ca(2+) oscillation in cultured cardiac myocytes from neonatal rats. To do this, we performed a noise analysis of fluctuations in the concentration of intracellular Mg(2+) in cardiac myocytes. The concentration was estimated by loading cells with either Mg-fluo4/AM or KMG-20/AM. Results revealed that the intensity of Mg-fluo-4 or KMG-20 fluorescence fluctuated cyclically in association with the rhythmic contraction of cardiac myocytes. In addition, the simultaneous measurement of Fura2 and Mg-fluo-4 fluorescence revealed phase differences between the dynamics of the two signals, suggesting that the cyclic changes in the Mg-fluo-4 or KMG-20 fluorescent intensity actually reflected the changes in intracellular Mg(2+). The complete termination of spontaneous rhythmic contractions did not abolish Mg(2+) oscillations, suggesting that the rhythmic fluctuations in intracellular Mg(2+) did not result from mechanical movements. We suggest that the concentration of intracellular Mg(2+) changes cyclically in association with spontaneous, cyclic changes in the concentration of intracellular Ca(2+) of cardiac myocytes. A noise analysis of the fluctuation of subtle changes in fluorescence intensity could contribute to the elucidation of novel functional roles of Mg(2+) in cells.
authors.affiliation: Laboratory of Cellular Cybernetics, Graduate School of Information Science and Technology, Hokkaido University, Sapporo, Japan. kawahara@ist.hokudai.ac.jp
authors.forename: Koichi
authors.initials: K
authors.lastname: Kawahara
authors.forename: Rie
authors.initials: R
authors.lastname: Sato
authors.forename: Sadahiro
authors.initials: S
authors.lastname: Iwabuchi
authors.forename: Daisuke
authors.initials: D
authors.lastname: Matsuyama
mesh_terms: D000814:Aniline Compounds / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000737:chemistry; D002474:Cell-Free System; D003593:Cytoplasm / Q000378:metabolism; D007477:Ions; D008274:Magnesium / Q000737:chemistry*; D009200:Myocardial Contraction; D009206:Myocardium / Q000378:metabolism; D032383:Myocytes, Cardiac / Q000166:cytology / Q000378:metabolism*; D009991:Oscillometry; D051381:Rats; D017208:Rats, Wistar; D013050:Spectrometry, Fluorescence / Q000379:methods; D013997:Time Factors; D014966:Xanthenes / Q000494:pharmacology
chemical_list: D000814:Aniline Compounds; C409648:Fluo 4; D007477:Ions; D014966:Xanthenes; D008274:Magnesium; D002118:Calcium