Figure 6. Indirect immunofluorescence of anti-sp32- and antiphosphotyrosine–double-labeled proteins in fixed porcine sperm. Sperm were incubated in noncapacitating conditions (A) and in capacitating conditions without (B) and with calcium ionophore A23187 (C) to provoke the acrosome reaction. Panels 1, 4, 7, and 10 are phase contrast, and fluorescent microscopy photographs of sperm are shown in Panels 2, 3, 5, 6, 8, 9, 11, and 12. The results showed labeling of both antibodies over the acrosomal region of capacitated sperm, which is consistent with the hypothesis that p32 is a tyrosine-phosphorylated form of sp32. Panels 8 and 9 show acrosome-reacted sperm. Secondary antibody only controls are presented in Panels 11 and 12. This experiment was repeated 4 times, and representative photographs are shown.