Abstract
We characterized and directly compared the Ca2+-releasing actions of two inhibitors of endoplasrnic-reticulum (ER) Ca2+-ATPase, thapsigargin and 2,5-di-(t-butyl)-1,4-benzohydro-quinone (tBuBHQ), in electropermeabilized insulin-secreting RINm5F cells. Ambient free calcium concentration ([Ca2+]) was monitored by Ca2+-selective mini-electrodes. After ATP-dependent Ca2+ uptake, thapsigargin and tBuBHQ released Ca2+ with an EC50 of ~ 37 nM and ~ 2 μM respectively. Both agents mobilized Ca2+ predominantly from the Ins(1,4,5)P3-sensitive Ca2+ pool, and in this respect thapsigargin was more specific than tBuBEIQ. The total increase in [Ca2+] obtained with thapsigargin and Ins(1,4,5)P3 was, on the average, only 7% greater than that with Ins(1,4,5)P3 alone. In contrast, the total increase in [Ca2+] obtained with tBuBHQ and Ins(1,4,5)P3 was 33 % greater than that obtained with only InsP3 (P < 0.05). Although Ca2+ was rapidly mobilized by thapsigargin and tBuBHQ,complete depletion of the Ins(1,4,5)P3-sensitive Ca2+ pool was difficult to achieve. After the release by thapsigargin or tBuBHQ, Ins(1,4,5)P3 induced additional Ca2+ release. The additional Ins(1,4,5)P3-induced Ca2+ release was not altered by supramaximal concentrations of thapsigargin and tBuBHQ, or by Bafilomycin A1, an inhibitor of V-type ATPases, but was decreased by prolonged treatment with the ER Ca2+-ATPase inhibitors. These results suggest the existence of distinct uptake and release compartments within the Ins(1,4,5)P3-sensitive Ca2+ pool. When treated with the inhibitors, the two compartments became distinguishable on the basis of their Ca2+ permeability. Apparently, thapsigargin and tBuBHQ readily mobilized Ca2+ from the uptake compartment, whereas Ca2+ from the release compartment could be mobilized only very slowly, in the absence of Ins(1,4,5)P3.
| Original language | English |
|---|---|
| Pages (from-to) | 423-429 |
| Number of pages | 7 |
| Journal | Biochemical Journal |
| Volume | 293 |
| Issue number | 2 |
| State | Published - Jan 1 1993 |
| Externally published | Yes |
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ASJC Scopus subject areas
- Biochemistry
Cite this
Mobilization of Ca2+ by thapsigargin and 2,5-di-(t-butyl)-1,4-benzohydroquinone in permeabilized insulin-secreting RlNm5F cells : Evidence for separate uptake and release compartments in inositol 1,4,5-trisphosphate-sensitive Ca2+ pool. / Islam Md., S.; Berggren, P. O.
In: Biochemical Journal, Vol. 293, No. 2, 01.01.1993, p. 423-429.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Mobilization of Ca2+ by thapsigargin and 2,5-di-(t-butyl)-1,4-benzohydroquinone in permeabilized insulin-secreting RlNm5F cells
T2 - Evidence for separate uptake and release compartments in inositol 1,4,5-trisphosphate-sensitive Ca2+ pool
AU - Islam Md., S.
AU - Berggren, P. O.
PY - 1993/1/1
Y1 - 1993/1/1
N2 - We characterized and directly compared the Ca2+-releasing actions of two inhibitors of endoplasrnic-reticulum (ER) Ca2+-ATPase, thapsigargin and 2,5-di-(t-butyl)-1,4-benzohydro-quinone (tBuBHQ), in electropermeabilized insulin-secreting RINm5F cells. Ambient free calcium concentration ([Ca2+]) was monitored by Ca2+-selective mini-electrodes. After ATP-dependent Ca2+ uptake, thapsigargin and tBuBHQ released Ca2+ with an EC50 of ~ 37 nM and ~ 2 μM respectively. Both agents mobilized Ca2+ predominantly from the Ins(1,4,5)P3-sensitive Ca2+ pool, and in this respect thapsigargin was more specific than tBuBEIQ. The total increase in [Ca2+] obtained with thapsigargin and Ins(1,4,5)P3 was, on the average, only 7% greater than that with Ins(1,4,5)P3 alone. In contrast, the total increase in [Ca2+] obtained with tBuBHQ and Ins(1,4,5)P3 was 33 % greater than that obtained with only InsP3 (P < 0.05). Although Ca2+ was rapidly mobilized by thapsigargin and tBuBHQ,complete depletion of the Ins(1,4,5)P3-sensitive Ca2+ pool was difficult to achieve. After the release by thapsigargin or tBuBHQ, Ins(1,4,5)P3 induced additional Ca2+ release. The additional Ins(1,4,5)P3-induced Ca2+ release was not altered by supramaximal concentrations of thapsigargin and tBuBHQ, or by Bafilomycin A1, an inhibitor of V-type ATPases, but was decreased by prolonged treatment with the ER Ca2+-ATPase inhibitors. These results suggest the existence of distinct uptake and release compartments within the Ins(1,4,5)P3-sensitive Ca2+ pool. When treated with the inhibitors, the two compartments became distinguishable on the basis of their Ca2+ permeability. Apparently, thapsigargin and tBuBHQ readily mobilized Ca2+ from the uptake compartment, whereas Ca2+ from the release compartment could be mobilized only very slowly, in the absence of Ins(1,4,5)P3.
AB - We characterized and directly compared the Ca2+-releasing actions of two inhibitors of endoplasrnic-reticulum (ER) Ca2+-ATPase, thapsigargin and 2,5-di-(t-butyl)-1,4-benzohydro-quinone (tBuBHQ), in electropermeabilized insulin-secreting RINm5F cells. Ambient free calcium concentration ([Ca2+]) was monitored by Ca2+-selective mini-electrodes. After ATP-dependent Ca2+ uptake, thapsigargin and tBuBHQ released Ca2+ with an EC50 of ~ 37 nM and ~ 2 μM respectively. Both agents mobilized Ca2+ predominantly from the Ins(1,4,5)P3-sensitive Ca2+ pool, and in this respect thapsigargin was more specific than tBuBEIQ. The total increase in [Ca2+] obtained with thapsigargin and Ins(1,4,5)P3 was, on the average, only 7% greater than that with Ins(1,4,5)P3 alone. In contrast, the total increase in [Ca2+] obtained with tBuBHQ and Ins(1,4,5)P3 was 33 % greater than that obtained with only InsP3 (P < 0.05). Although Ca2+ was rapidly mobilized by thapsigargin and tBuBHQ,complete depletion of the Ins(1,4,5)P3-sensitive Ca2+ pool was difficult to achieve. After the release by thapsigargin or tBuBHQ, Ins(1,4,5)P3 induced additional Ca2+ release. The additional Ins(1,4,5)P3-induced Ca2+ release was not altered by supramaximal concentrations of thapsigargin and tBuBHQ, or by Bafilomycin A1, an inhibitor of V-type ATPases, but was decreased by prolonged treatment with the ER Ca2+-ATPase inhibitors. These results suggest the existence of distinct uptake and release compartments within the Ins(1,4,5)P3-sensitive Ca2+ pool. When treated with the inhibitors, the two compartments became distinguishable on the basis of their Ca2+ permeability. Apparently, thapsigargin and tBuBHQ readily mobilized Ca2+ from the uptake compartment, whereas Ca2+ from the release compartment could be mobilized only very slowly, in the absence of Ins(1,4,5)P3.
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UR - http://www.scopus.com/inward/citedby.url?scp=0027181188&partnerID=8YFLogxK
M3 - Article
AN - SCOPUS:0027181188
VL - 293
SP - 423
EP - 429
JO - Biochemical Journal
JF - Biochemical Journal
SN - 0264-6021
IS - 2
ER -