PKC activity??

[Lin Xiao]

I have a question about the stability of PKC in cells. According to some 
papers, PKC can lost the activity quickly so that the sample should be 
kept in an ice or at -20C or with 50% of glycerol and the assay should be 
performed without delay. I'm trying to test the activity on fresh human 
neutrophils. Could I keep the sample at -20C or -70C for longer time with or 
whitout glycerol ?? Any suggestion?

Thanks

Lin