Table 2.

Ca²⁺ release in response to IP₃ at different stages of maturation^a

Developmental stageb	Fluorescence after UV exposurec
Stage VI oocyte	0.4 ± 0.2 (6)
At GVBD	0.4 ± 0.2 (6)
1 h after GVBD	0.45 ± 0.2 (6)
2 h after GVBD	0.5 ± 0.2 (6)
3 h after GVBD (mature egg)	0.7 ± 0.2* (6)

^a Data are expressed as the mean ± S.D. n = number of eggs tested. 

^b Stage VI oocytes were coinjected with 20-μM Ca²⁺ green dextran and 1-μM caged IP₃. Stage VI oocytes and oocytes collected at various time points after progesterone addition were exposed to 5- or 10-s UV light to uncage the IP₃ and Ca²⁺ green fluorescence was monitored as in Figure 8. In each experimental run, the amount of UV used to uncage the IP₃ was determined by finding the shortest time of UV exposure that could induce Ca²⁺ release in mature eggs (in each experimental run, oocytes and eggs were exposed to UV for the same amount of time). 

^c Data for Ca²⁺ green fluorescence in response to IP₃ are expressed as the area under the curve of photomultiplier current as a function of time for a 6-min period after the UV exposure; these values were normalized by dividing by (baseline current × 6 min). Data are presented this way rather than as peak amplitudes, because the peak sometimes occurred during the UV exposure. 

^* This value is significantly different from the control value obtained from stage VI oocytes (unpaired t test, p < 0.02).