PBS with or without Calcium and Magnesium - When it is important to use either one in Cell culture?? (Apr/23/2008 )

Hey all,
I have been wondering about the PBS with Magnesium and Calcium and without - when one should use either when approaching cell culture? What is the role of both salts in Cell culture?
Thanks for your time,
CHG

We generally use PBS without salts..But, I have read it depends on the cell line. When you are trypsining cells, you do not want any divalent ions, as apparently they inhibit trypsin action. so when you wash with PBS it removes the residues and your trypsin has EDTA in it which chelates away any divalent ions present. The divalent ions are originally present in your media and FCS also has protease inhibitors in it. That why it is ok to directly pippete cells aftrer trypsinisation without bothering much about removing the trypsin.

Definitely without both ions (salts) cupidstorm is right. Both ions can inhibit trypsin reaction.