Figure 4. The [Ca²⁺]_i in human sperm induced by rhuZP3a²²¹⁷⁶ (A) or rhuZP3b¹⁷⁷³⁴⁸ (B). [Ca²⁺]_i was calculated by the ratio of fluorescence intensity at the two excitation wavelengths (340 / 380 nm) (emission 510 nm). The arrow represents the time at which rhuZP3a²²¹⁷⁶ or rhuZP3b¹⁷⁷³⁴⁸ was added. The solid line shows the Fura-2/AM-loaded sperm plus rhuZP3a²²¹⁷⁶ or rhuZP3b¹⁷⁷³⁴⁸. Pimozide (100 µM) was added to Fura-2/AM-loaded sperm 10 minutes before the addition of rhuZP3a²²¹⁷⁶ or rhuZP3b¹⁷⁷³⁴⁸ (dotted line). EGTA (2 mM) was added to Fura-2/AM loaded sperm 10 minutes before the addition of rhuZP3a²²¹⁷⁶ or rhuZP3b¹⁷⁷³⁴⁸ (dashed line).