Na+/Ca2+ exchange in rat osteoblast-like UMR 106 cells

Kenneth E. White, Frank A. Gesek, Peter A. Friedman

Research output: Contribution to journalArticle

10 Scopus citations

Abstract

Ca2+ efflux from osteoblasts is thought to be mediated by Na+/Ca2+ exchange and by a plasma membrane Ca2+-ATPase. The presence of plasma membrane Na+/Ca2+ exchange was determined in rat UMR 106 osteosarcoma cells by functional and molecular studies. Na+/Ca2+ exchange activity was tested by measuring changes of [Ca2+](i) in single cells. After Na+ loading the cells and removing extracellular Na+, the direction of exchange was reversed and [Ca2+](i) increased by 100%. Multiple isoforms of the NCX1 gene product, encoding plasma membrane Na+/Ca2+ exchangers, were cloned from UMR 106 cells and a sample of primary human osteoblasts using homology-based RT-PCR. Isoforms NACA3, NACA7, and NACA10 were found in UMR 106 cells, whereas human osteoblasts expressed NACA3 and NACA7. Transcripts for NCX2 and the Na+/Ca2+, K+ exchanger were not detected. Northern analysis of UMR 106 cells with a probe to the NCX1 gene product revealed the presence of a transcript of 7 kb, the size of the exchanger message. Western analysis of UMR 106 cell membrane preparations with a polyclonal antibody specific for the NCX1 exchanger showed the presence of reacting proteins consistent with the reported masses of the exchanger at 125 and 85 kD. These results demonstrate Na+-dependent Ca2+ efflux from UMR 106 cells and the presence of several NACA isoforms in UMR 106 and primary human osteoblasts.

Original languageEnglish (US)
Pages (from-to)1666-1675
Number of pages10
JournalJournal of Bone and Mineral Research
Volume11
Issue number11
StatePublished - Nov 1 1996
Externally publishedYes

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Orthopedics and Sports Medicine

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