How to denaturate protein for ELISA - (Oct/27/2009 )

Hi, I have overexpressed my protein in a cell line and have collected the media to study the secretion of my protein. How could i use Urea or guanidine hydrocloride to denaturate my samples before ELISA? Or what other method could I use to denaturate my protein?
Thank you

Usually 6 or 8M urea or Gu HCl shoyld do the trick but I am not sure if it will interfere in the ELISA!!!