Goudeau H, Depresle Y, Rosa A, Goudeau M
Station Biologique de Roscoff, UPR C.N.R.S. 4601, Roscoff, France.
Dev Biol. 1994 Dec;166(2):489-501. doi: 10.1006/dbio.1994.1332.
Eggs of the ascidian Phallusia mammillata were voltage clamped (from -100 to +60 mV) and inseminated with a low or heavy sperm concentration. From inseminations with low sperm concentration (1 x 10(6) sp/ml), we found that fertilization currents occurred between -100 and +40 mV: they were always inward and displayed an analogous pattern whatever the clamped voltage. We established that the percentages of inseminated eggs that produced a fertilization current varied as a function of the clamped voltage. These percentages were not statistically different from 100% at clamped voltages between -100 and -30 mV, they decreased to 68 and 56% at clamped Vm of -10 and 0 mV, respectively, but were not statistically different from 0% at clamped Vm between +10 and +40 mV. We never obtained any egg electrical response at a clamped voltage of +50 mV. Almost all eggs (96%) which responded electrically were penetrated by one or several spermatozoa. These eggs were resuming meiosis (81 to 50%) at values of clamped Vm between -100 and 0 mV, respectively. At clamped Vm between +10 and +50 mV, the percentages of eggs resuming meiosis were not statistically different from 0. These results indicate that in P. mammillata eggs, the occurrence of an electrical response is voltage dependent and consequently that the initial depolarizing shift of the fertilization potential constitutes a fast block to polyspermy. However, in this species, the sperm penetration is not voltage dependent, since it occurred at clamped Vm from -100 to +40 mV. On the other hand, when eggs were clamped from -100 to +60 mV and inseminated with a heavy sperm concentration (2 x 10(7) sp/ml), the curves expressing, respectively, the percentages of eggs which responded electrically, the percentages of eggs which were penetrated by one or several spermatozoa, and the percentages of eggs resuming meiosis, as functions of the clamped Vm, were shifted by approximately 35 mV toward more positive voltages, compared to the corresponding curves obtained from eggs inseminated with a low sperm concentration. This last result means that the critical value of the membrane potential which characterizes the electrical block to polyspermy is dependent on the sperm concentrations used for inseminations.
对海鞘乳头海鞘的卵进行电压钳制（从-100到+60 mV），并用低精子浓度或高精子浓度进行受精。在低精子浓度（1×10⁶个精子/毫升）的受精实验中，我们发现受精电流出现在-100到+40 mV之间：它们总是内向电流，并且无论钳制电压如何，都呈现出类似的模式。我们确定产生受精电流的受精卵百分比随钳制电压而变化。在钳制电压为-100到-30 mV之间时，这些百分比与100%无统计学差异，在钳制膜电位为-10 mV和0 mV时，分别降至68%和56%，但在钳制膜电位为+10到+40 mV之间时，与0%无统计学差异。在钳制电压为+50 mV时，我们从未获得任何卵的电反应。几乎所有产生电反应的卵（96%）都被一个或几个精子穿透。这些卵在钳制膜电位分别为-100到0 mV时恢复减数分裂（81%到 50%）。在钳制膜电位为+10到+50 mV之间时，恢复减数分裂的卵的百分比与0%无统计学差异。这些结果表明，在乳头海鞘的卵中，电反应的发生依赖于电压，因此受精电位的初始去极化转变构成了对多精受精的快速阻断。然而，在这个物种中，精子穿透不依赖于电压，因为它发生在钳制膜电位从-100到+40 mV时。另一方面，当卵从-1_{00}到+60 mV进行电压钳制并用高精子浓度（2×10⁷个精子/毫升）进行受精时，分别表示产生电反应的卵百分比、被一个或几个精子穿透的卵百分比以及恢复减数分裂的卵百分比作为钳制膜电位函数的曲线，与用低精子浓度受精的卵得到的相应曲线相比，向更正的电压方向移动了约35 mV。最后这个结果意味着表征对多精受精电阻断的膜电位临界值取决于用于受精的精子浓度。
