Fig. 4. Relationship between intracellular and extracellular calcium. Spermatozoa were incubated in either complete BWW or BWW -Ca²⁺ as indicated. Approximately 40 minutes before the time shown, 10x10⁶ cells were harvested and loaded with 2 µM FURA 2. Following a 20-minute incubation, the cells were centrifuged, washed and the [Ca²⁺]_i was determined as described in Materials and Methods. This graph represents the data from three experiments performed in duplicate.