title: Effect of hyperglycemia on the changes of intracellular [Ca2+]i in heart myoblast.
abstract: A rise in cytosolic free Ca2+ is the immediate trigger for contraction in heart muscle. In the present study, we investigated changes of intracellular Ca2+ increased by potassium chloride (KCl) and phenylephrine (PE) under hyperglycemia in rat heart myoblast H9c2 cells (BCRC 60096), respectively. We employed the fluorescent Ca2+-indicator, fura-2, and digital imaging microscopy to measure [Ca2+]i in H9c2 cells. Cells were cultured in hyperglycemic (30 mM glucose) Dulbecco's Modified Eagle's Medium. The variation of [Ca2+]i induced by KCI and PE in hyperglycemia was examined, respectively. Moreover, tiron, one of the antioxidants, was pretreated in hyperglycemia-treated H9c2 cells to measure the role of free radicals in the changes of intracellular [Ca2+]i. An influx in intracellular Ca2+ induced by KCl or PE was observed in a dose-dependent manner and reached the highest concentration of 434 +/- 42.3 nM and 443 +/- 42.8 nM (n = 24 cells), respectively. Moreover, this increase of intracellular [Ca2+]i induced by KCl or PE was markedly reduced in cells exposed to hyperglycemia (434 +/- 42.3 vs. 1.26 +/- 0.21 nM and 443 +/- 42.8 vs. 2.54 +/- 0.25 nM, n = 24 cells, P < 0.001, respectively). Similar changes were not observed in cells received mannitol showing same osmolarity. However, the reduction of intracellular [Ca2+]i induced by hyperglycemia was abolished significantly in the presence of tiron. Our results suggest that an increase of intracellular Ca2+ by KCl or PE in heart cell was markedly reduced by hyperglycemic treatment; mediation of free radicals in this action can be considered because it was reversed in the presence of tiron.
authors.affiliation: Department of Medical Research, Kuang-Tien General Hospital, Taichung 43353, Taiwan, Republic of China.
authors.forename: Nai-Yuan
authors.initials: NY
authors.lastname: Lee
authors.forename: Ming-Hui
authors.initials: MH
authors.lastname: Sun
authors.forename: Wang-Sheng
authors.initials: WS
authors.lastname: Ko
mesh_terms: D014013:1,2-Dihydroxybenzene-3,5-Disulfonic Acid Disodium Salt / Q000494:pharmacology; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002316:Cardiotonic Agents / Q000494:pharmacology; D002478:Cells, Cultured; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D006943:Hyperglycemia / Q000378:metabolism*; D032386:Myoblasts, Cardiac / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D010656:Phenylephrine / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats
chemical_list: D000975:Antioxidants; D002316:Cardiotonic Agents; D010656:Phenylephrine; D014013:1,2-Dihydroxybenzene-3,5-Disulfonic Acid Disodium Salt; D011189:Potassium Chloride; D002118:Calcium