Divalent cation involvement in the action of Clostridium perfringens type A enterotoxin.  Early events in enterotoxin action are divalent cation-independent. 
Clostridium perfringens type A enterotoxin (CPE) is a membrane-active cytotoxin.  There are a number of recognized early steps in CPE cytotoxicity including binding of CPE to a protein receptor, insertion of CPE into membranes, and CPE-mediated induction of changes in membrane permeability for small molecules such as ions and amino acids.  Further support for the existence of these early steps and further characterization of these events are presented in this report.  We now report that these early steps in CPE action are largely independent of extracellular divalent cations.  It is also shown that 3H-nucleotide release, known to be a later CPE effect, is Ca2+-dependent.  A model for CPE cytotoxicity is suggested involving CPE action as a two-step process with Ca2+-independent early steps and Ca2+-dependent late steps.