Fig. 7.

Redistribution of IP₃R1 during oocyte maturation. (A and B) Oocytes were labeled with IP₃R1 and imaged by confocal microcopy. The observations were performed at 0, 4, 8 and 12 hr of maturation, which corresponded with GV, GVBD, MI and MII stages. Oocytes were matured in the absence (A) or in the presence of 5 µM colcemid (B; upper panel) or 2.5 µM Lat-A (B; lower panel). A typical equatorial section is shown. Scale bar, 30 µm. (C) IP₃-induced Ca²⁺ release using cIP₃ was examined in control (solid line) and colcemid-treaded (dashed line) GVBD oocytes. The 0.001 sec UV pulse was applied to oocytes (open arrow). The number of oocytes responding to cIP₃ is shown in parentheses. (D) Oocytes were matured for 8 hr in the absence of LatA, cIP₃ was injected at this time, after which maturation continued for 4 hr in the absence or presence of LatA. IP₃-induced Ca²⁺ release using cIP₃ was examined in control MII (solid line) and LatA-treaded MI arrested (dashed line) oocytes. The 0.001 sec UV pulse was applied to oocytes (open arrow). The number of oocytes responding to cIP₃ is shown in parentheses.