Mobilization of 45Ca from insulin-producing RINm5F cells attached to microcarriers.

H. Abrahamsson, P. O. Berggren, B. Hellman

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10 Scopus citations


A technique was designed allowing studies of 45Ca efflux from insulin-releasing cells of a clonal cell line (RINm5F) attached to fibronectin-coated plastic beads. Supporting the existence of Ca2+-Ca2+ and Na+-Ca2+ exchange mechanisms, the efflux of 45Ca in a Ca2+-deficient perifusion medium was increased after introduction of Ca2+ and decreased after removal of Na+. The washout of radioactivity was similar to that from pancreatic islets in also being inhibited by glucose in the presence of low concentrations of extracellular Ca2+. During perifusion with a medium containing 2.56 mM Ca2+, increasing the K+ concentration resulted in an increased 45Ca efflux, a process counteracted by D-600. Also, exposure to tolbutamide resulted in a distinct stimulatory peak. Glucose was a poor stimulator of 45Ca efflux, suggesting that this sugar lacks the ability to depolarize the RINm5F cells sufficiently to induce normal opening of the voltage-dependent channels in the plasma membrane. Such a defect might well explain why the RINm5F cells do not respond to glucose with stimulation of insulin release.

Original languageEnglish (US)
Pages (from-to)E719-725
JournalThe American journal of physiology
Issue number6 Pt 1
StatePublished - Dec 1984

ASJC Scopus subject areas

  • Physiology (medical)


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