Intracellular pH and the sodium requirement at fertilisation
Intracellular pH and the sodium requirement at fertilisation
复制标题
受精时细胞内 pH 值和钠需求
作者：
S. Shen;R. Steinhardt
一些证据表明，离子信使是受精过程中代谢抑制的主要因素。在受精或孤雌基因激活海胆卵的抑制发生在两个主要阶段。第一阶段触发受精的早期事件，由细胞内游离钙的短暂增加介导。第二个触发受精后期事件，是由细胞内pH值升高介导的（参考文献4-6）。从早期的海胆卵受精过程过渡到后期的过程，需要在外部培养基中加入最低浓度的钠。受精后的酸流出需要外部Na+。在一个假设中，Na+需求和酸流出是相关的，该假设提出内部质子被交换为外部Na+（参考文献8,9）。通过使用pH敏感微电极，我们更密切地研究了外部Na+与内部pH之间的关系。我们在这里证明，卵子激活后细胞内pH值的增加确实需要外部Na+。然而，卵细胞浆的碱化对外部Na+的大量减少相对不敏感，这是反对Na - h交换假说的证据。
Several lines of evidence suggest that ionic messengers are primary agents in the metabolic derepression which occurs at fertilisation. The derepression at fertilisation or partheno-genetic activation of the sea urchin egg occurs in two main phases. The first phase, which triggers the early events of fertilisation, is mediated by transitory increase of intracellular free calcium1–3. The second, which triggers the late events of fertilisation, is mediated by a rise in the intracellular pH (refs 4–6). The transition from the early events of fertilisation of sea urchin eggs to the late events requires a minimal concentration of sodium in the external medium7. External Na+ is required for the acid efflux which follows fertilisation8. Na+ requirement and the acid efflux have been correlated in a hypothesis which proposes that internal protons are exchanged for external Na+ (refs 8, 9). By using pH-sensitive microelectrodes, we have examined the relationship between external Na+ and internal pH more closely. We demonstrate here that the increase of the intracellular pH following egg activation does require external Na+. However, the relative insensitivity of the alkalisation of the egg cytoplasm to large reductions of external Na+ is evidence against the Na–H exchange hypothesis.