title: Na+-Ca2+ exchanger modulates Ca2+ content in intracellular Ca2+ stores in rat osteoblasts.
abstract: Na+-Ca2+ exchanger (NCX) transports Ca2+ coupled with Na+ across the plasma membrane in a bi-directional mode. Ca2+ flux via NCX mediates osteogenic processes, such as formation of extracellular matrix proteins and bone nodules. However, it is not clearly understood how the NCX regulates cellular Ca2+ movements in osteogenic processes. In this study, the role of NCX in modulating Ca2+ content of intracellular stores ([Ca2+]ER) was investigated by measuring intracellular Ca2+ activity in isolated rat osteoblasts. Removal of extracellular Na+ elicited a transient increase of intracellular Ca2+ concentration ([Ca2+]i). Pretreatment of antisense oligodeoxynucleotide (AS) against NCX depressed this transient Ca2+ rise and raised the basal level of [Ca2+]i. In AS-pretreated cells, the expression and activity of alkaline phosphatase (ALP), an osteogenic marker, were decreased. However, the cell viability was not affected by AS-pretreatment. Suppression of NCX activity by the AS-pretreatment decreased ATP-activated Ca2+ release from intracellular stores and significantly enhanced Ca2+ influx via store operated calcium influx (SOCI), compared to those of S-pretreated or control cells. These results strongly suggest that NCX has a regulatory role in cellular Ca2+ pathways in osteoblasts by modulating intracellular Ca2+ content.
authors.affiliation: Department of Physiology and Biophysics, Center for Advanced Medical Education by BK21 Project, Inha University College of Medicine, Incheon 402-751, Korea.
authors.forename: Sang Yong
authors.initials: SY
authors.lastname: Jung
authors.forename: Yong Joo
authors.initials: YJ
authors.lastname: Park
authors.forename: Young Jun
authors.initials: YJ
authors.lastname: Park
authors.forename: Seok Ho
authors.initials: SH
authors.lastname: Cha
authors.forename: Myung Za
authors.initials: MZ
authors.lastname: Lee
authors.forename: Chang Kook
authors.initials: CK
authors.lastname: Suh
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002470:Cell Survival; D002478:Cells, Cultured; D003593:Cytoplasm / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D042541:Intracellular Space / Q000378:metabolism; D020319:Oligodeoxyribonucleotides, Antisense / Q000494:pharmacology; D010006:Osteoblasts / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D015398:Signal Transduction; D012964:Sodium / Q000502:physiology; D019831:Sodium-Calcium Exchanger / Q000502:physiology*
chemical_list: D020319:Oligodeoxyribonucleotides, Antisense; D019831:Sodium-Calcium Exchanger; D012964:Sodium; D000469:Alkaline Phosphatase; D002118:Calcium