Fig. 2. Effects of low Ca²⁺ seawater (LCaSW), D-600, and heparin on sperm-induced Ca²⁺ changes. The oocyte where 10 kDa CGD was injected into the cytoplasm was preincubated for 6-8 minutes in LCaSW (A), in FSW containing 100 µM D-600 (B), or in LCaSW containing 100 µM D-600 (C), and then inseminated. In D, the oocyte injected with 10 kDa CGD plus 20 mg/ml heparin was inseminated in FSW. The F/F₀ values were calculated in the cytoplasmic and nuclear regions separately (A,D) or in the whole oocyte (B,C). GVBD was prominently delayed (occurred at 25 minutes after fertilization) in A, or prevented in B and C. In contrast, GVBD took place on schedule in D.