myo-Inositol 1,4,5-trisphosphate mobilizes Ca2+ from isolated adipocyte endoplasmic reticulum but not from plasma membranes.
myo-Inositol 1,4,5-trisphosphate mobilizes Ca2+ from isolated adipocyte endoplasmic reticulum but not from plasma membranes.
复制标题
肌醇 1,4,5-三磷酸从分离的脂肪细胞内质网动员 Ca2，但不从质膜动员 Ca2。
DOI：
10.1042/bj2360037
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发表时间：
1986
期刊：
影响因子：
--
通讯作者：
McDonald,JM
中科院分区：
文献类型：
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作者：
Delfert,DM;Hill,S;Pershadsingh,HA;Sherman,WR;McDonald,JM
研究了肌醇1,4,5-三磷酸（IP3）对离体脂肪细胞内质网和质膜囊Ca2+摄取和释放的影响。IP3的作用最初是用含有胞浆的内质网制剂（S1-ER）来表征的。在钒酸盐存在的情况下，IP3对S1-ER囊泡Ca2+释放的最大和半最大影响分别发生在20微米-IP3和7微米-IP3时，钒酸盐可以阻止释放的Ca2+通过内质网Ca2+泵的再摄取。在饱和IP3浓度下，钒酸盐存在时Ca2+释放量为可交换Ca2+池的20%。ip3诱导的Ca2+从S1-ER释放依赖于囊外游离Ca2+浓度，最大释放发生在0.13 microM游离Ca2+。在20微米- ip3下，S1-ER对Ca2+的初始摄取速率没有影响。与S1-ER相比，IP3促进离体内质网囊泡（细胞质不存在）的Ca2+释放达到相似水平。向离体内质网囊泡添加细胞质溶胶不影响ip3诱导的Ca2+释放。内质网制剂经差速离心进一步分离为重、轻囊泡。有趣的是，当IP3刺激时，重质组分释放Ca2+，而轻质组分则没有。IP3（20微米）不促进Ca2+从质膜囊泡释放，对(Ca2+ + Mg2+)- atp酶活性和这些囊泡对atp依赖性Ca2+摄取的初始速率没有影响。这些结果支持IP3仅作用于内质网促进Ca2+释放的概念。
The effects of myo-inositol 1,4,5-trisphosphate (IP3) on Ca2+ uptake and release from isolated adipocyte endoplasmic reticulum and plasma membrane vesicles were investigated. Effects of IP3 were initially characterized using an endoplasmic reticulum preparation with cytosol present (S1-ER). Maximal and half-maximal effects of IP3 on Ca2+ release from S1-ER vesicles occurred at 20 microM- and 7 microM-IP3, respectively, in the presence of vanadate which prevents the re-uptake of released Ca2+ via the endoplasmic reticulum Ca2+ pump. At saturating IP3 concentrations, Ca2+ release in the presence of vanadate was 20% of the exchangeable Ca2+ pool. IP3-induced release of Ca2+ from S1-ER was dependent on extravesicular free Ca2+ concentration with maximal release occurring at 0.13 microM free Ca2+. At 20 microM-IP3 there was no effect on the initial rate of Ca2+ uptake by S1-ER. IP3 promoted Ca2+ release from isolated endoplasmic reticulum vesicles (cytosol not present) to a similar level as compared with S1-ER. Addition of cytosol to isolated endoplasmic reticulum vesicles did not affect IP3-induced Ca2+ release. The endoplasmic reticulum preparation was further fractionated into heavy and light vesicles by differential centrifugation. Interestingly, the heavy fraction, but not the light fraction, released Ca2+ when challenged with IP3. IP3 (20 microM) did not promote Ca2+ release from plasma membrane vesicles and had no effect on the (Ca2+ + Mg2+)-ATPase activity or on the initial rate of ATP-dependent Ca2+ uptake by these vesicles. These results support the concept that IP3 acts exclusively at the endoplasmic reticulum to promote Ca2+ release.