Conrad G W, Glackin P V, Hay R A, Patron R R
Division of Biology, Kansas State University, Manhattan 66506.
J Exp Zool. 1987 Aug;243(2):245-58. doi: 10.1002/jez.1402430210.
We have studied the ability of fertilized eggs of Ilyanassa obsoleta to undergo polar lobe formation and cytokinesis in the presence of Ca2+ antagonists (Ca2+ channel blockers, Ca2+ uptake inhibitors). Earlier work had suggested little need for exogenous Ca2+ during these cellular shape changes. Again it appears that exogenous Ca2+ probably is not required, based on cell ability to undergo the shape changes with no, or only minor, delay in the presence of 50 mM La3+ at pH 6.5, 10 mM concentrations of Ni2+ or Co2+, 1 mM Cd2+, and 100 microM concentrations of Mn2+, papaverine, verapamil, D600, or diltiazem. In nominally Ca2+-free seawater (containing approximately 10 microM Ca2+) (CFSW), there still is no effect of Cd2+ (up to 100 microM), Ni2+, Co2+, Mn2+, or diltiazem; however, papaverine, verapamil, and D600 in CFSW cause longer delays in the shape changes than they do in the presence of normal levels of Ca2+ (SW). In 10-50 microM nifedipine, shape changes are progressively delayed to the same extent in both SW and CFSW, but more so in CFSW at concentrations above 50 microM nifedipine. Among calmodulin antagonists, trifluoperazine up to 100 microM was without effect, but chlorpromazine at 25-100 microM and calmidazolium at 50-100 microM caused substantial, concentration-dependent delays in the starting times for the shape changes. Methylxanthines caused a substantial speed-up in the starting times for both polar lobe formation and cytokinesis. The most effective of these, caffeine, at optimal concentrations of 0.7-10 mM in SW or CFSW caused shape changes to occur 12-15 min earlier than in controls undergoing a normal 50-min cycle. Caffeine is known to cause release of Ca2+ from muscle sarcoplasmic reticulum. A putative antagonist of intracellular Ca2+ mobilization, TMB-8, significantly inhibited the shape changes of the Ilyanassa cells, whereas a variety of inhibitors of exogenous Ca2+ uptake noted above did not inhibit. We conclude that Ca2+ may be necessary for polar lobe formation and cytokinesis in Ilyanassa cells, but that it may be released from intracellular, sequestered stores rather than derived from exogenous sources.
我们研究了在存在Ca2 +拮抗剂（Ca2 +通道阻滞剂、Ca2 +摄取抑制剂）的情况下，过时泥蚶受精卵进行极叶形成和胞质分裂的能力。早期的研究表明，在这些细胞形态变化过程中对外源Ca2 +的需求很少。同样，基于细胞在pH 6.5的50 mM La3 +、10 mM浓度的Ni2 +或Co2 +、1 mM Cd2 +以及100 microM浓度的Mn2 +、罂粟碱、维拉帕米、D600或地尔硫卓存在下能够无延迟或仅轻微延迟地进行形态变化的能力，似乎外源Ca2 +可能并非必需。在名义上无Ca2 +的海水（含有约10 microM Ca2 +）（无钙海水，CFSW）中，Cd2 +（高达100 microM）、Ni2 +、Co2 +、Mn2 +或地尔硫卓仍然没有影响；然而，CFSW中的罂粟碱、维拉帕米和D600比在正常Ca2 +水平（海水，SW）存在时导致形态变化的延迟更长。在10 - 50 microM硝苯地平中，SW和CFSW中的形态变化均逐渐延迟至相同程度，但在硝苯地平浓度高于50 microM时，CFSW中的延迟更明显。在钙调蛋白拮抗剂中，高达100 microM的三氟拉嗪没有作用，但25 - 100 microM的氯丙嗪和50 - 100 microM的卡米达唑引起形态变化起始时间的显著、浓度依赖性延迟。甲基黄嘌呤使极叶形成和胞质分裂的起始时间大幅加快。其中最有效的咖啡因，在SW或CFSW中的最佳浓度为0.7 - 10 mM时，使形态变化比正常50分钟周期的对照提前12 - 15分钟发生。已知咖啡因会导致肌肉肌浆网释放Ca2 +。一种假定的细胞内Ca2 +动员拮抗剂TMB - 8显著抑制了过时泥蚶细胞的形态变化，而上述各种外源Ca2 +摄取抑制剂则没有抑制作用。我们得出结论，Ca2 +可能是过时泥蚶细胞极叶形成和胞质分裂所必需的，但它可能从细胞内储存中释放出来，而不是来源于外源。
