Fig. 4. PtdIns(4,5)P₂ synthesis at fertilization is Ca²⁺-dependent. (A) Changes in [Ca²⁺]_i and PH-GFP distribution recorded at fertilization in an egg pretreated with 1 µM BAPTA-AM. Similar results were obtained in 15 eggs. (B) Upper panel, changes in [Ca²⁺]_i and PH-GFP distribution elicited by uncaging Ins(1,4,5)P₃ using a low UV power (0.5% excitation-indicated by the horizontal bar). Similar results were obtained in eight eggs. Lower panel, changes in [Ca²⁺]_i and PH-GFP distribution elicited by uncaging Ins(1,4,5)P₃ using a tenfold higher UV power (5% excitation-indicated by the horizontal bar). Similar results were obtained in five eggs. For abbreviations, see Fig. 2 legend.