Fig. 1. Ca²⁺ requirement for the maintenance of human sperm motility and viability. Motile sperm selected using glass wool columns were incubated for up to 18 hours at 37°C in medium not supplemented with CaCl₂ (–Ca²⁺, ), or containing different concentrations of CaCl₂: 0.22 mM (), 0.58 mM (), 1.5 mM () or 2.5 mM (). The percentages of progressively motile (A) and live (B) cells after 1, 2, 4, 6 and 18-hour incubation were determined as described in Materials and Methods. The results are expressed as mean±s.e.m., n=7. *P<0.05 when compared to sperm motility under all other conditions.