Due to ionic changes in permeability of the surface membrane of the newly fertilized egg. Injection of IP 3 into the egg can also induce the cortical granule reaction in sea urchins and in hamsters.
C b are second messengers.
The IP 3 is then rapidly dephosphorylated by a phosphatase. DAG is rapidly broken apart. Protein kinase C can activate other cellular molecules, including transcription factors. These cause other late events in egg activation following fertilization, as shown below. Increase in intracellular pH from 6.8 to 7.2.