Stachecki J J, Armant D R
Department of Obstetrics and Gynecology, C.S. Mott Center for Human Growth and Development, Wayne State University School of Medicine, Detroit, MI 48201, USA.
Development. 1996 Aug;122(8):2485-96. doi: 10.1242/dev.122.8.2485.
Inositol 1,4,5-trisphosphate can regulate growth and differentiation by modulating the release of intracellular Ca2+ in a variety of cellular systems, and it is involved in oocyte activation. Recent studies suggest that mammalian preimplantation development may also be regulated by the release of Ca2+ from intracellular stores. The rate of cavitation and cell division was accelerated after a transient elevation of intracellular Ca2+ levels was induced in morulae by exposure to ethanol or ionomycin. Embryos exposed to BAPTA-AM, a chelator of intracellular Ca2+, exhibited a brief dose-dependent reduction in basal Ca2+ levels, a temporal inhibition of ionophore-induced Ca2+ signalling and a subsequent delay in blastocoel formation. BAPTA-AM at 0.5 microM did not significantly alter the basal intracellular calcium level, but chelated Ca2+ that was released after ethanol exposure and thereby attenuated the ethanol-induced acceleration of cavitation. BAPTA-AM also inhibited cell division to the 16-cell stage in a dose-dependent manner, which correlated with the inhibition of cavitation. Thimerosal and inositol 1,4,5-trisphosphate significantly elevated the intracellular Ca2+ concentration in mouse morula-stage embryos, providing evidence for the existence of inositol 1,4,5-trisphosphate-sensitive Ca2+ stores. Although caffeine failed to release intracellular Ca2+, ryanodine induced a small biphasic release of Ca2+, suggesting that ryanodine-sensitive Ca2+ stores may also exist in mouse embryos. Morulae exposed to the calmodulin inhibitor W-7 exhibited a dose-dependent delay in blastocoel formation. A 4 hour exposure to 10 microM W-7 did not significantly alter cavitation, but attenuated the ionophore-induced stimulation of blastocoel formation. This finding suggests that the developmental effects produced through Ca2+ signalling are mediated by calmodulin. Our results demonstrate that Ca2+ release in mouse morulae occurs predominantly through the inositol 1,4,5-trisphosphate receptor, and that alteration of intracellular Ca2+ levels can accelerate or delay embryonic growth and differentiation, providing a mechanistic link between the regulation of oocyte and embryonic development.
肌醇1,4,5 - 三磷酸可通过调节多种细胞系统中细胞内Ca2+的释放来调控生长和分化，并且它参与卵母细胞激活。最近的研究表明，哺乳动物着床前发育可能也受细胞内钙库释放Ca2+的调控。通过暴露于乙醇或离子霉素诱导桑椹胚细胞内Ca2+水平短暂升高后，空泡化和细胞分裂速率加快。暴露于细胞内Ca2+螯合剂BAPTA - AM的胚胎，其基础Ca2+水平呈现短暂的剂量依赖性降低，对离子载体诱导的Ca2+信号传导有暂时抑制作用，随后胚泡腔形成延迟。0.5微摩尔的BAPTA - AM并未显著改变基础细胞内钙水平，但螯合了乙醇暴露后释放的Ca2+，从而减弱了乙醇诱导的空泡化加速。BAPTA - AM还以剂量依赖性方式抑制细胞分裂至16细胞期，这与空泡化抑制相关。硫柳汞和肌醇1,4,5 - 三磷酸显著提高了小鼠桑椹胚期胚胎的细胞内Ca2+浓度，为肌醇1,4,5 - 三磷酸敏感的Ca2+储存库的存在提供了证据。尽管咖啡因未能释放细胞内Ca2+，但ryanodine诱导了Ca2+的小幅度双相释放，表明ryanodine敏感的Ca2+储存库可能也存在于小鼠胚胎中。暴露于钙调蛋白抑制剂W - 7的桑椹胚在胚泡腔形成上呈现剂量依赖性延迟。暴露于10微摩尔W - 7 4小时并未显著改变空泡化，但减弱了离子载体诱导的胚泡腔形成刺激。这一发现表明，通过Ca2+信号传导产生的发育效应是由钙调蛋白介导的。我们的结果表明，小鼠桑椹胚中的Ca2+释放主要通过肌醇1,4,5 - 三磷酸受体发生，并且细胞内Ca2+水平的改变可加速或延迟胚胎生长和分化，为卵母细胞和胚胎发育的调控之间提供了一个机制联系。
