TY - JOUR
T1 - Mobilization of calcium by inositol trisphosphates from permeabilized rat parotid acinar cells. Evidence for translocation of calcium from uptake to release sites within the inositol 1,4,5-trisphosphate- and thapsigargin-sensitive calcium pool
AU - Menniti, F S
AU - Bird, G S
AU - Takemura, H
AU - Thastrup, Ole
AU - Potter, B V
AU - Putney, J W
PY - 1991
Y1 - 1991
N2 - D-myo-Inositol (1,4,5)-trisphosphate ((1,4,5)IP3)-induced Ca2+ release and subsequent Ca2+ reuptake were investigated in saponin-permeabilized rat parotid acinar cells. Following the rapid release of Ca2+ by (1,4,5)IP3, Ca2+ was resequestered. The sequential addition of submaximal concentrations of (1,4,5)IP3 resulted in sequential Ca2+ release. However, when the cells were challenged with the poorly metabolized (1,4,5)IP3 analogues, (1,4,5)IPS3 or (2,4,5)IP3, or under conditions where the metabolism of authentic (1,4,5)IP3 was reduced, Ca2+ reuptake again occurred, but sequestered Ca2+ was not released by subsequent additions of (1,4,5)IP3. The sequestered Ca2+ was, however, released by thapsigargin, an agent which inhibits active Ca2+ uptake into the (1,4,5)IP3-sensitive pool. Furthermore, the rate of thapsigargin-induced release was significantly increased in the continued presence of an (1,4,5)IP3 stimulus. Thus, Ca2+ reuptake apparently occurred into the (1,4,5)IP3- and thapsigargin-sensitive Ca2+ store and (1,4,5)IP3 continued to influence the permeability of this pool to Ca2+ during Ca2+ reuptake. In contrast to the findings in permeabilized cells, Ca2+ reuptake did not occur in the sustained presence of (1,4,5)IP3 in intact parotid cells. We conclude that cell permeabilization reveals a kinetic, and presumably structural, separation of Ca2+ uptake and release sites within the (1,4,5)IP3-regulated intracellular organelle.
AB - D-myo-Inositol (1,4,5)-trisphosphate ((1,4,5)IP3)-induced Ca2+ release and subsequent Ca2+ reuptake were investigated in saponin-permeabilized rat parotid acinar cells. Following the rapid release of Ca2+ by (1,4,5)IP3, Ca2+ was resequestered. The sequential addition of submaximal concentrations of (1,4,5)IP3 resulted in sequential Ca2+ release. However, when the cells were challenged with the poorly metabolized (1,4,5)IP3 analogues, (1,4,5)IPS3 or (2,4,5)IP3, or under conditions where the metabolism of authentic (1,4,5)IP3 was reduced, Ca2+ reuptake again occurred, but sequestered Ca2+ was not released by subsequent additions of (1,4,5)IP3. The sequestered Ca2+ was, however, released by thapsigargin, an agent which inhibits active Ca2+ uptake into the (1,4,5)IP3-sensitive pool. Furthermore, the rate of thapsigargin-induced release was significantly increased in the continued presence of an (1,4,5)IP3 stimulus. Thus, Ca2+ reuptake apparently occurred into the (1,4,5)IP3- and thapsigargin-sensitive Ca2+ store and (1,4,5)IP3 continued to influence the permeability of this pool to Ca2+ during Ca2+ reuptake. In contrast to the findings in permeabilized cells, Ca2+ reuptake did not occur in the sustained presence of (1,4,5)IP3 in intact parotid cells. We conclude that cell permeabilization reveals a kinetic, and presumably structural, separation of Ca2+ uptake and release sites within the (1,4,5)IP3-regulated intracellular organelle.
KW - Animals
KW - Calcium
KW - Cell Compartmentation
KW - Cell Membrane Permeability
KW - Cells, Cultured
KW - Diphosphoglyceric Acids
KW - Egtazic Acid
KW - Heparin
KW - Inositol 1,4,5-Trisphosphate
KW - Kinetics
KW - Organelles
KW - Parotid Gland
KW - Rats
KW - Terpenes
KW - Thapsigargin
KW - Time Factors
M3 - Journal article
C2 - 1906881
SN - 0021-9258
VL - 266
SP - 13646
EP - 13653
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 21
ER -