Premium
Interaction with the inositol 1,4,5‐trisphosphate receptor promotes Ca 2+ sequestration in permeabilised insulin‐secreting cells
Author(s) -
Islam Md.Shahidul,
Nilsson Thomas,
Rorsman Patrik,
Berggren Per-Olof
Publication year - 1991
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(91)80995-f
Subject(s) - inositol , steady state (chemistry) , chemistry , reuptake , calcium , stimulation , receptor , inositol phosphate , medicine , endocrinology , biophysics , biochemistry , biology , serotonin , organic chemistry
Electropermeabilised insulin‐secreting RINm5F cells sequestered Ca 2+ , resulting in a steady‐state level of the ambient free Ca 2+ 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)P 3 ) promoted a rapid and pronounced release of Ca 2+ . This Ca 2+ was resequestered and a new steady‐state Ca 2+ level was attained, which was always lower (460 ± 102 nM, n = 10, P < 0.001) than the steady‐state Ca 2+ level maintained before the addition of Ins(1,4,5)P 3 . Whereas the initial reuptake of Ca 2+ subsequent to Ins(1,4,5,)P 3 stimulation was relatively slow, the later part of reuptake was fast as compared to the reuptake phases of a pulse addition of extraneous Ca 2+ . In the latter case the uptake of Ca 2+ resulted in a steady‐state level similar to that found in the absence of Ins(1,4,5)P 3 . Addition of Ins(1,4,5)P 3 under this condition resulted in a further Ca 2+ uptake and thus a lower steady‐state Ca 2+ level, Heparin, which binds to the Ins(1,4,5)P 3 receptor, also lowered the steady‐state free Ca 2+ concentration, In contrast to Ins(1,4,5)P 3 inositol 1,3,4,5‐tetrakis‐phosphate was without effect on Ca 2+ sequestration. These findings are consistent with the presence of a high‐affinity Ins(1,4,5)P 3 receptor promoting continuous release of Ca 2+ under basal conditions and/or the Ins(1,4,5)P 3 receptor being actively involved in Ca 2+ sequestration.