A highly localized activation current yet widespread intracellular calcium increase in the egg of the frog, Discoglossus pictus.
A highly localized activation current yet widespread intracellular calcium increase in the egg of the frog, Discoglossus pictus.
复制标题
青蛙卵中高度局部化的激活电流但广泛的细胞内钙增加。
DOI：
10.1016/0012-1606(88)90419-8
复制
发表时间：
1988
影响因子：
2.7
通讯作者：
Campanella,C
中科院分区：
文献类型：
--
作者：
Nuccitelli,R;Kline,D;Busa,WB;Talevi,R;Campanella,C
精子进入彩蛙（Discoglossus pictus）的卵子，只发生在动物半球的一个特殊区域，称为动物酒窝，这种结构在其他种类的青蛙中没有发现。细胞外振动电极用于测量激活电流，以确定打开以产生受精电位的离子通道是否位于该区域。通过显微注射1，4，5-三磷酸肌醇（Ins（1，4，5）P3）激活的卵表现出与受精卵非常相似的激活电位。在注射Ins（1，4，5）P3的时间和激活电位的启动之间存在延迟，该延迟与激活刺激位点和动物酒窝之间的距离成比例，类似于先前在刺激活卵中观察到的延迟（R.塔莱维，B。Dale和C. 03 The Dog（1985）111，316 -323）。当刺激部位与动物酒窝成20°（300 μm）时，延迟持续30秒，当刺激部位与动物酒窝成150°时，延迟持续14分钟。一旦激活电位被启动，去极化时间和第一个可检测到的电流进入凹坑区域的时间之间有很好的时间相关性。这种向内电流的幅度通常为60 μA/cm 2，仅在酒窝区域的中心200 μm处发现。外向电流分布在鸡蛋表面的其余部分，幅度小得多。激活电流由动物窝区的Cl−流出携带，并被DIDS降低，并被高外部Cl−或I−逆转。向内电流只出现在凹坑区域，这表明Cl−通道是局部化的，这些通道打开产生激活电位。用Ca ~（2+）特异性微电极观察到，受精和激活后卵母细胞内[Ca ~（2+）] i均从0.25 μ M增加到2 μ M，约37 min后恢复到未激活水平。用振动探针研究了pictus，发现这些细胞的内向电流远小于激活卵的内向电流。在卵母细胞的整个动物脑半球和植物脑半球都有一个稳定的跨细胞电流，电流密度可达4 μA/cm 2。
Sperm entry in the egg of the painted frog,Discoglossus pictus, occurs only at a specialized region of the animal hemisphere called the animal dimple, a structure not found in other species of frog. An extracellular vibrating electrode was used to measure the activation current to determine if the ion channels that open to generate the fertilization potential are localized in this region. Eggs that were activated by microinjecting inositol-1,4,5-trisphosphate (Ins(1,4,5)P3) exhibited activation potentials very similar to those of fertilized eggs. There was a delay between the time of Ins(1,4,5)P3injection and the initiation of the activation potential that was proportional to the distance between the site of the activating stimulus and the animal dimple, similar to the delay previously observed in prick-activated eggs (R. Talevi, B. Dale, and C. Campanella (1985).Dev. Biol.111,316–323). The delay lasted 30 sec when the stimulus site was 20° (300 μm) from the animal dimple and 14 min when it was 150° from the dimple. Once the activation potential was initiated, there was an excellent temporal correlation between the time of depolarization and the time of the first detectable current entering the dimple region. This inward current was typically 60 μA/cm2in amplitude and was found only in the central 200 μm of the dimple region. The outward current was distributed over the remainder of the egg surface and was much smaller in amplitude. The activation current was carried by Cl−efflux in the animal dimple region, and was reduced by DIDS and reversed by high external Cl−or I−. The occurrence of inward current only at the dimple region indicates that Cl−channels which open to produce the activation potential are localized there. Using Ca2+-specific microelectrodes, we found that [Ca2+]iincreased from 0.25 to 2 μMfollowing both fertilization and activation and returned to the unactivated level after about 37 min. Immature oocytes ofD. pictuswere also studied with the vibrating probe and the inward current in these cells was much less localized than that in the activating egg. A steady transcellular current of up to 4 μA/cm2entered the entire animal hemisphere of the oocyte and exited the vegetal hemisphere.