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Interaction with the inositol 1,4,5-trisphosphate receptor promotes Ca2+ sequestration in permeabilised insulin-secreting cells
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Sciences, Internal Medicine.
1991 (English)In: FEBS Letters, ISSN 0014-5793, E-ISSN 1873-3468, Vol. 288, no 1-2, 27-29 p.Article in journal (Refereed) Published
Abstract [en]

Electropermeabilised insulin-secreting RINm5F cells sequestered Ca2+, resulting in a steady-state level of the ambient free Ca2+ concentration corresponding to 723 +/- 127 nM (mean +/- SEM, n = 10), as monitored by a Ca(2+)-selective minielectrode. Inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) promoted a rapid and pronounced release of Ca2+. This Ca2+ was resequestered and a new steady-state Ca2+ level was attained, which was always lower (460 +/- 102 nM, n = 10, P less than 0.001) than the steady-state Ca2+ level maintained before the addition of Ins(1,4,5)P3. Whereas the initial reuptake of Ca2+ subsequent to Ins(1,4,5)P3 stimulation was relatively slow, the later part of reuptake was fast as compared to the reuptake phases of a pulse addition of extraneous Ca2+. In the latter case the uptake of Ca2+ resulted in a steady-state level similar to that found in the absence of Ins(1,4,5)P3. Addition of Ins(1,4,5)P3 under this condition resulted in a further Ca2+ uptake and thus a lower steady-state Ca2+ level. Heparin, which binds to the Ins(1,4,5)P3 receptor, also lowered the steady-state free Ca2+ concentration. In contrast to Ins(1,4,5)P3, inositol 1,3,4,5-tetrakisphosphate was without effect on Ca2+ sequestration. These findings are consistent with the presence of a high-affinity Ins(1,4,5)P3 receptor promoting continuous release of Ca2+ under basal conditions and/or the Ins(1,4,5)P3 receptor being actively involved in Ca2+ sequestration.

Place, publisher, year, edition, pages
1991. Vol. 288, no 1-2, 27-29 p.
National Category
Medical and Health Sciences
URN: urn:nbn:se:uu:diva-132307DOI: 10.1016/0014-5793(91)80995-FPubMedID: 1652478OAI: oai:DiVA.org:uu-132307DiVA: diva2:357428
Available from: 2010-10-18 Created: 2010-10-18 Last updated: 2010-10-26Bibliographically approved

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