I am working with a 4T1 mouse breast cancer model and I want to digest the lungs to culture for lung mets. The protocol says to add "30 units of elastase" to my collagenase IV solution that I am using to digest the lungs. I have elastase powder but I cannot figure out what to do with it.

How do I know what 30 units of elastase is? Do I need to dissolve the elastase in something before I add it to the collagenase solution and if so what do I dissolve it in? What concentration should it be dissolved to?

I cannot find the answers to this anywhere. The bottle does not say what a unit is, only that there are "≥8 units per mg protein." Most articles I've found that used elastase either don't say how much they used or they say something like "3 U/mL" which does not help me because I still don't know how to determine what a unit is.

If anyone has ever used elastase before, please tell me how you figured out how much to use?