Fig. 1.

Zn²⁺ changes Em and increases pH_i and [Ca²⁺]_i as FSP and Speract.

Em (upper row records), pHi (middle row records) and [Ca²⁺]_i (lower row records) of sea urchin sperm were measured in cell populations as described in methods. Dotted lines indicate a point of agonist addition: A, Zn²⁺ (10 M total); B, FSP (~100 nmol fucose/ml); C, 100 nM Speract. The free concentration of Zn²⁺ was estimated to be 0.2 nM in Em measurement (0.8 mM EDTA) and 1.8 nM in pH_i and [Ca²⁺]_i measurements (0.1 mM EDTA). Downward and upward deflections of each parameter indicate hyperpolarization and depolarization of Em and decreases and increases of [Ca²⁺]_i and pH_i, respectively. The scale of each parameter Em (mV), pH_i (FAU, Fluorescence Arbitrary Units) and [Ca²⁺]_i ((F/F0); where F is Fluo-4 (or Quin-2) fluorescence intensity and F0 is the fluorescence before adding speract or Zn²⁺) is indicated with vertical bars. The time scale was indicated by horizontal bars. Records shown in this figure are representative of at least three different animals. Zn²⁺ and FSP induced similar amounts of acrosome reaction that were ≥57%.