AN ELECTRICAL BLOCK IS REQUIRED TO PREVENT POLYSPERMY IN EGGS FERTILIZED BY NATURAL MATING OF XENOPUS-LAEVIS
AN ELECTRICAL BLOCK IS REQUIRED TO PREVENT POLYSPERMY IN EGGS FERTILIZED BY NATURAL MATING OF XENOPUS-LAEVIS
复制标题
DOI：
10.1016/0012-1606(82)90335-9
复制
发表时间：
1982-01-01
影响因子：
2.7
通讯作者：
SCHERTEL, ER
中科院分区：
文献类型：
--
作者：
GREY, RD;BASTIANI, MJ;SCHERTEL, ER
在27%的德波尔盐水（DBS）中，产生最大的生育率，体外受精的爪蟾卵是单精子的，无论精子浓度如何。如前所述，多精受精的一个阻滞（缓慢阻滞）发生在受精被膜上，该受精被膜响应皮质反应而升高。一个早期的，快速的块在质膜的属性进行了描述，并在自然交配条件下的生理精子浓度的2块的功能意义进行了评价。未受精卵在27% DBS中的静息膜电位为-19 mV。受精触发快速去极化至+8mV（受精电位，FP）;该电位保持为正。用离子载体A23187 [calcimycin]激活卵子，产生较慢但相似的去极化（激活电位，AP）。与其他两栖类卵一样，FP似乎是Cl-净流出的结果，因为FP（或离子载体激活卵中的AP）的峰值随着培养基中氯盐浓度的增加而降低。在67%的DBS中，没有观察到FP或AP;在67%的DBS中受精的卵子变成多精子，平均每个卵子有2个精子进入位点。在5-37 mM范围内，I-和Br-，而不是F-，在产生多精受精方面比Cl-更有效。在20 mM碘化钠，质膜超极化响应精子或离子载体; 100%水平的多精受精和平均14个精子进入每个鸡蛋的网站进行了观察。NaI不抑制或延迟受精膜的升高;皮质反应和受精膜在透射电镜下是正常的。在67%的DBS中，它也抑制快阻滞，慢阻滞估计在授精后6-8分钟起作用。在20 mM NaI中自然交配受精的卵子表现出50-90%的多精受精水平，每个卵子平均有5个精子进入位点。由于在抑制多精受精的快速而非缓慢阻断的条件下，卵子通过自然交配受精时成为多精受精，因此快速阻断对于在卵子通常遇到的精子浓度下防止多精受精至关重要。
In 27% DeBoer''s saline (DBS), which yields maximum fertility rates, Xenopus eggs fertilized in vitro are monospermic, regardless of sperm concentration. One block to polyspermy (the slow block), described previously, occurs at the fertilization envelope that is elevated in response to the cortical reaction. Properties of an earlier, fast block at the plasma membrane are described and the functional significance of the 2 blocks at physiological sperm concentrations in natural mating conditions is evaluated. Unfertilized eggs have a resting membrane potential of -19 mV in 27% DBS. Fertilization triggers a rapid depolarization to +8 mV (the fertilization potential, FP); the potential remains positive for .apprx. 15 min. Activation of eggs with the ionophore, A23187, [calcimycin], produces a slower but similar depolarization (the activation potential, AP). As in other amphibian eggs, the FP appears to result from a net efflux of Cl-, since the peak of the FP (or the AP in ionophore-activated eggs) decreases as the concentration of chloride salts in the medium is increased. In 67% DBS no FP or AP is observed; eggs fertilized in 67% DBS become polyspermic and average 2 sperm entry sites per egg. In the 5-37 mM range, I- and Br-, but not F-, are more effective than Cl- in producing polyspermy. In 20 mM NaI, the plasma membrane hyperpolarizes in response to sperm or ionophore; 100% levels of polyspermy and an average of 14 sperm entry sites per egg are observed. NaI does not inhibit or retard elevation of the fertilization envelope; the cortical reaction and fertilizatin envelope are normal in transmission electron micrographs. In 67% DBS, which also inhibits the fast block, the slow block was estimated to become functional 6-8 min after insemination. Eggs fertilized by natural mating in 20 mM NaI exhibit polyspermy levels of 50-90% and average 5 sperm entry sites per egg. Since eggs become polyspermic when fertilized by natural mating under conditions that inhibit the fast, but not the slow, block to polyspermy, the fast block is essential to the prevention of polyspermy at the sperm concentrations normally encountered by the egg.