Roubos E W, Schmidt E D, Moorer-van Delft C M
Cell Tissue Res. 1981;215(1):63-73. doi: 10.1007/BF00236249.
The ultrastructural dynamics of exocytosis in the ovulation-stimulating neurosecretory Caudo-Dorsal Cells (CDC) of the freshwater snail L. stagnalis were studied after incubation of cerebral ganglia in Ringer's solutions with different concentrations of K+ and Ca2+. Detection of exocytosis was facilitated by the use of the tannic acid-glutaraldehyde fixation method (TAGO-method). In control Ringer (low K+) the frequency of exocytosis was rather low. Exocytosis mainly occurred as "terminal" exocytosis (TE); "intracellular" (ICE) and, particularly, "multiple" exocytosis (ME) took place infrequently. Incubation in high K+-containing Ringer strongly increased exocytotic activity. Compared to the controls the total frequency of exocytosis was 50 X as high, whereas TE, ICE and ME occurred 6 X, 47 X, and more than 300 X as frequently, respectively. In high K+/Ca2+-free Ringer the total frequency of exocytosis was only 2 X as high as in control Ringer. It is concluded that TE, ICE, and ME are normal, Ca2+-dependent exocytotic phenomena. The significance of their dynamics in response to K+-stimulation is discussed. The extremely high frequency of exocytosis, as well as the presence of "unaltered granule contents in transit", is explained by assuming that an exocytotic event in the CDC lasts rather long, viz. some minutes. The results may reflect the physiological mechanism by which the CDC release their ovulation hormone. The possible involvement of "clear" and "large" electron lucent vesicles in membrane reuptake after exocytosis is considered.
在将淡水蜗牛静水椎实螺的脑神经节于含有不同浓度K⁺和Ca²⁺的林格氏液中孵育后，研究了排卵刺激神经分泌尾背细胞（CDC）胞吐作用的超微结构动力学。使用单宁酸 - 戊二醛固定法（TAGO法）有助于检测胞吐作用。在对照林格氏液（低钾）中，胞吐作用的频率相当低。胞吐作用主要以“终末”胞吐（TE）的形式发生；“细胞内”（ICE），特别是“多次”胞吐（ME）很少发生。在含高K⁺的林格氏液中孵育会强烈增加胞吐活性。与对照组相比，胞吐作用的总频率高出50倍，而TE、ICE和ME发生的频率分别高出6倍、47倍和300倍以上。在高K⁺/无Ca²⁺的林格氏液中，胞吐作用的总频率仅为对照林格氏液中的2倍。得出的结论是，TE、ICE和ME是正常的、依赖Ca²⁺的胞吐现象。讨论了它们对K⁺刺激的动力学响应的意义。通过假设CDC中的胞吐事件持续相当长的时间，即几分钟，来解释胞吐作用的极高频率以及“转运中未改变的颗粒内容物”的存在。这些结果可能反映了CDC释放排卵激素的生理机制。考虑了“清亮”和“大”的电子透明小泡在胞吐作用后膜再摄取中的可能参与。
