Marker for cell death?

[N.Ambalavanan MD]

I am trying to find if a peptide found in conditioned media is secreted 
by living cells or is a fragment of dying cells. Can someone inform me 
what would be a good marker for cell death -enzyme etc that will be 
detectable and quantifiable in conditioned media? This is assuming cell 
number, trypan blue exclusion remain stable in underlying cells.Or are 
there any other techniques? Please email me - Thank you!