CALCIUM ENTRY IN XENOPUS OOCYTES - EFFECTS OF INOSITOL TRISPHOSPHATE, THAPSIGARGIN AND DMSO
CALCIUM ENTRY IN XENOPUS OOCYTES - EFFECTS OF INOSITOL TRISPHOSPHATE, THAPSIGARGIN AND DMSO
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DOI：
10.1016/0143-4160(93)90080-p
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发表时间：
1993-02-01
期刊：
影响因子：
4
通讯作者：
ORON, Y
中科院分区：
文献类型：
--
作者：
LUPUMEIRI, M;BEITOR, A;ORON, Y
激动剂和肌醇1,4,5-三磷酸（InsP3）在非洲爪蟾卵母细胞中引起的反应利用从细胞储存和培养基中动员的钙。我们研究了钙储存状态对insp3诱导的钙进入的影响。Thapsigargin （TG）以时间和剂量依赖的方式引起卵母细胞Ca-45（2+）流出的净增加（分别占总标记的31%和54%，在30和60分钟）。用TG孵育（60分钟）导致对InsP3的反应完全丧失，这意味着对InsP3敏感的Ca储存被耗尽。1.8 mM Ca2+激发产生了一个大的去极化氯离子电流（1231 +/- 101 nA），而这一电流没有被InsP3进一步增强。这表明细胞内钙储存的大量消耗足以诱导细胞外钙（Ca(o)）的最大进入。注射了InsP3后，细胞内钙离子的损失非常有限，足以产生大量的钙离子。单独二甲亚砜（DMSO），用于溶解TG的载体，不会导致45 Ca2+的外排增加，也不会增加Ca(o)诱发的Cl-电流，但在注射InsP3后，它确实显着增强了该电流。DMSO适度抑制insp3诱导的Ca-45（2+）从卵母细胞流出。因此，可以观察到钙进入的明显增强，而无需额外的细胞钙消耗。我们得出的结论是，钙的进入可能是通过用InsP3和有限的钙消耗刺激或单独消耗特定的、可能很小的细胞钙储存来诱导的。DMSO增强的机制尚不清楚，但鉴于这种溶剂作为媒介的普遍使用，可能是重要的。
Agonist- and inositol 1,4,5-trisphosphate (InsP3)-evoked responses in Xenopus oocytes utilize calcium mobilized from cellular stores as well as from the medium. We studied the effect of the status of Ca stores on InsP3-induced Ca entry. Thapsigargin (TG) caused a net increase of Ca-45(2+) efflux from oocytes in a time and dose dependent manner (31 and 54% of total label, at 30 and 60 min, respectively). Incubation with TG (60 min) resulted in a complete loss of the response to InsP3 implying that InsP3-sensitive Ca stores were depleted. Challenge with 1.8 mM Ca2+ resulted in a large depolarizing chloride current (1231 +/- 101 nA) which was not further potentiated by InsP3. This suggested that extensive depletion of cellular Ca stores is sufficient to induce maximal entry of extracellular Ca (Ca(o)). Following the injection of InsP3, a much more limited loss of cellular Ca was sufficient to produce large Ca entry. Dimethyl sulfoxide (DMSO) alone, the vehicle used to dissolve TG, did not cause increase in either efflux of 45 Ca2+, nor in the Ca(o)-evoked Cl- current It did, however, markedly potentiate this current following the injection of InsP3. DMSO moderately inhibited InSP3-induced Ca-45(2+) efflux from oocytes. Hence, apparent potentiation of Ca entry can be observed without additional depletion of cellular Ca. We conclude that Ca entry may be induced via either stimulation with InsP3 and limited Ca depletion or depletion of a specific and, possibly small, cellular Ca store alone. The mechanism of DMSO potentiation is unknown, but may be important in view of the universal use of this solvent as vehicle.