Kazazoglou T, Schackmann R W, Fosset M, Shapiro B M
Proc Natl Acad Sci U S A. 1985 Mar;82(5):1460-4. doi: 10.1073/pnas.82.5.1460.
As a prerequisite to fertilization, sea urchin sperm undergo an acrosome reaction that is mediated in part by increased permeability to Ca2+, with an attendant rapid, massive intracellular Ca2+ accumulation. The acrosome reaction is inhibited by Ca2+ channel antagonists, including verapamil, D600, and dihydropyridines such as nitrendipine, nimodipine, and nisoldipine. To examine the interaction of Ca2+ antagonists with sperm, a plasma membrane preparation enriched for Na+,K+-ATPase was isolated from sea urchin sperm. These plasma membranes specifically bound [3H]nitrendipine and [3H]verapamil at concentrations similar to those that inhibit the acrosome reaction. The binding of verapamil was sigmoidal and half-maximal at 1 microM. There was a high specificity in the binding interaction, since by competition binding verapamil, (-)-D600, and (+)-D600 had different relative Kd values, 11, 2.5, and 0.5 microM, respectively. These data suggest that sperm mediate the Ca2+ influx required for induction of the acrosome reaction via Ca2+ channels with properties similar, but not identical, to those of other excitable tissues.
作为受精的前提条件，海胆精子会经历顶体反应，该反应部分由对Ca2+通透性增加介导，伴随着细胞内Ca2+迅速大量积累。顶体反应受到Ca2+通道拮抗剂的抑制，包括维拉帕米、D600以及二氢吡啶类药物，如尼群地平、尼莫地平和尼索地平。为了研究Ca2+拮抗剂与精子的相互作用，从海胆精子中分离出富含Na+,K+-ATP酶的质膜制剂。这些质膜在与抑制顶体反应相似的浓度下特异性结合[3H]尼群地平和[3H]维拉帕米。维拉帕米的结合呈S形，在1 microM时达到半数最大结合。结合相互作用具有高度特异性，因为通过竞争结合，维拉帕米、(-)-D600和(+)-D600具有不同的相对解离常数（Kd）值，分别为11、2.5和0.5 microM。这些数据表明，精子通过与其他可兴奋组织性质相似但不完全相同的Ca2+通道介导顶体反应诱导所需的Ca2+内流。
