FLASH FREEZING AND ENZYME WORK INQUIRY - (May/02/2012 )

Hi!
I'm just starting work on a Na/K-ATPase assay in gill samples. BUT I have a question about tissue storage:

If I collect fresh gill samples and want to freeze them for later use, do they NEED to be flash frozen in liquid nitrogen before going into the -80 freezer? Or if I freeze the samples directly in the -80 (more gradually) will the assay still work, even though there may be cell damage?

I've already frozen them (without using N2) but it's not too late to get more gill samples if people don't think it'll work - far better to get more samples than waste the materials for the assay.
But better yet, does anyone know if it will still work without flash freezing? Thanks a lot in advance - this is one mistake I won't be making twice.

Actually, just talked to someone in my lab - he's done this assay before without liquid nitrogen (wasn't available) - as long as you keep the sample on ice then put it directly into the freezer, it should be okay (the cell damage apparently isn't enough to ruin the assay).
Thanks anyway - hope this answers anyone else with the same question...