Freeman G, Ridgway E B
Friday Harbor Laboratories, University of Washington, Austin, Texas.
Dev Biol. 1993 Mar;156(1):176-90. doi: 10.1006/dbio.1993.1068.
A calcium transient occurs at fertilization in the eggs of the hydrozoans Mitrocomella and Phialidium. The eggs of Phialidium have an intracellular pH (pHi) of 7.6-7.95. There is no increase in pHi following fertilization. Both calcium ionophore and ammonia treatments activate Phialidium eggs. Calcium ionophore causes a calcium transient without changing pHi. Ammonia concentrations of 10-20 mM at pH 8 cause a rise in pHi but no detectable calcium transient. Both activating agents can (1) block subsequent fertilization, (2) initiate cell cycle events such as DNA synthesis, nuclear envelope breakdown, chromosome condensation, and cleavage-related events, and (3) initiate voltage-dependent calcium channel function. While calcium ionophore treatment invariably elicits all of these manifestations of egg activation, ammonia sometimes induces only the induction of voltage-dependent calcium channel function. Oocytes were also treated with calcium ionophore or ammonia at different stages during their maturation. Ammonia treatment did not induce egg activation when applied at any stage during maturation; however, calcium ionophore initiated voltage-dependent calcium channel function when oocytes were treated after germinal vesicle breakdown. Ionophore treatment during maturation did not render these eggs unfertilizable or initiate cell cycle events. These experiments show that elevation of [Ca2+] with ionophore and increasing pHi with ammonia may activate these eggs through different pathways, that specific maturational events must occur before they can do so, and that the activation of voltage-dependent calcium channel function can be dissociated from other egg activation events.
在水螅虫纲的米氏水母属（Mitrocomella）和瓶状水母属（Phialidium）的卵受精时会发生钙瞬变。瓶状水母属的卵细胞内pH值（pHi）为7.6 - 7.95。受精后pHi没有升高。钙离子载体和氨处理都能激活瓶状水母属的卵。钙离子载体可引起钙瞬变而不改变pHi。pH值为8时，10 - 20 mM的氨浓度会使pHi升高，但未检测到钙瞬变。两种激活剂都能（1）阻止后续受精，（2）引发细胞周期事件，如DNA合成、核膜破裂、染色体凝聚以及与卵裂相关的事件，（3）引发电压依赖性钙通道功能。虽然钙离子载体处理总是会引发卵激活的所有这些表现，但氨有时仅诱导电压依赖性钙通道功能。卵母细胞在成熟的不同阶段也用钙离子载体或氨进行处理。在成熟过程中的任何阶段施加氨处理都不会诱导卵激活；然而，当卵母细胞在生发泡破裂后用钙离子载体处理时，会引发电压依赖性钙通道功能。成熟过程中用离子载体处理不会使这些卵无法受精或引发细胞周期事件。这些实验表明，用离子载体升高[Ca2+]和用氨升高pHi可能通过不同途径激活这些卵，在它们能够激活之前必须发生特定的成熟事件，并且电压依赖性钙通道功能的激活可以与其他卵激活事件分离。
