Figure 1.

Ca²⁺ oscillations and uncaging pulses of InsP₃. In (A) an example trace is shown of Ca²⁺ increases (as measured by OGBD fluorescence) in an egg in response to different amounts of InsP₃. Eggs were injected with caged InsP₃ and exposed to varying durations of UV light pulse (from 50 ms to 2 s) to photo-release the InsP₃ (trace typical of n = 21 eggs). In this and all other traces shown, the pulses were applied at points indicated by the arrows. In (B) an example trace is shown of changes in cytosolic Ca²⁺ in an egg in response to the “uncaging” of caged InsP3 using long duration UV pulses of 3 s. Arrows indicate where pulses of UV light were applied (typical of n = 7 eggs). In (C) an example trace is shown of changes in cytosolic Ca²⁺ in an egg stimulated following the microinjection of mouse derived PLCζ cRNA (0.02 μg/μl) and caged InsP₃. The arrow indicates where a 100 ms pulse of UV light was applied (n = 14 eggs). In all 14/14 such recordings there was no sudden increase in Ca²⁺ even when the pulse was applied during the pacemaker rising phase of Ca²⁺. In (D) an example trace is shown with changes in cytosolic Ca²⁺ in an egg stimulated by media containing 10 mM Sr²⁺. The arrow indicates where a 100 ms pulse of UV light was applied to uncage InsP₃ (n = 32 eggs). In all 32/32 cases there was a rapid Ca²⁺ increase that started with the very next OGBD fluorescence measurement after the UV pulse (<10 s).