Exp Mol Med.  2007 Aug;39(4):458-468.

Na+-Ca2+ exchanger modulates Ca2+ content in intracellular Ca2+ stores in rat osteoblasts

• Jung SY
• Park YJ
• Park YJ
• Cha SH
• Lee MZ
• Suh CK

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.

Keyword

calcium; osteoblasts; sodium-calcium exchanger

MeSH Terms

Alkaline Phosphatase/metabolism
Animals
Calcium/*metabolism
Cell Membrane/metabolism
Cell Survival
Cells, Cultured
Cytoplasm/metabolism
Endoplasmic Reticulum/metabolism
Intracellular Space/metabolism
Oligodeoxyribonucleotides, Antisense/pharmacology
Osteoblasts/drug effects/*physiology
Rats
Signal Transduction
Sodium/physiology
Sodium-Calcium Exchanger/*physiology