Schütt W, Sackin H
Department of Physiology and Biophysics, Cornell University, Medical College, 1300 York Ave., New York, NY 10021, USA.
Pflugers Arch. 1997 Jan;433(3):368-75. doi: 10.1007/s004240050290.
A new technique is described for evaluating the volume sensitivity of both endogenous and expressed ion channels in Xenopus oocytes. The technique utilizes vesicles derived from inside-out, excised patches and permits evaluation of volume sensitivity at the single-channel level, which is not possible with whole oocytes since removal of the vitelline membrane renders oocytes too fragile to withstand osmotic stress. Using this method, the volume sensitivity of the normally occurring oocyte mechanosensitive (SA-cat) channel was assessed. In 12 experiments, osmotic swelling increased vesicle volume by an average of 60 +/- 8% and increased the surface area of the inner side of the vesicle by 47 +/- 10%. This was associated with an increase in mean number of open channels (NPo) from zero (unswollen) to 0.1 +/-0.02 (after 5 min). Hence, oocyte SA-cat channels are volume as well as stretch sensitive, where the volume sensitivity may involve cytoskeletal elements adhering to the membrane but probably does not involve freely diffusible components of the original oocyte.
本文描述了一种评估非洲爪蟾卵母细胞内源性和表达离子通道体积敏感性的新技术。该技术利用由内向外切除的膜片衍生的囊泡，能够在单通道水平评估体积敏感性，而对于完整的卵母细胞则无法做到这一点，因为去除卵黄膜后卵母细胞过于脆弱，无法承受渗透压应激。使用该方法，评估了正常存在的卵母细胞机械敏感性（SA-cat）通道的体积敏感性。在12次实验中，渗透性肿胀使囊泡体积平均增加60±8%，使囊泡内侧表面积增加47±10%。这与开放通道的平均数量（NPo）从零（未肿胀）增加到0.1±0.02（5分钟后）相关。因此，卵母细胞SA-cat通道对体积和拉伸均敏感，其中体积敏感性可能涉及附着于膜的细胞骨架成分，但可能不涉及原始卵母细胞中可自由扩散的成分。
