Effects of divalent cations on adhesiveness of rat polymorphonuclear neutrophils in vitro

Cell preparations rich in polymorphonuclear neutrophils (PMN) were obtained from peritoneal exudates of rats without the use of any anticoagulant. The adhesiveness of these PMN to glass bead columns coated with rat serum were studied quantitatively using suspending solutions free of added serum protein. A dependence of the PMN adhesiveness upon divalent cations was demonstrated. Added singly Mg²⁺, Ni²⁺, Zn²⁺, Co²⁺, Mn²⁺, Cu²⁺, or Cd²⁺ were found to be effective whereas Ca²⁺, Sr²⁺ and Ba²⁺ were ineffective. A possible auxilliary role for Ca²⁺ when added with Mg²⁺ is suggested by the data. The ineffectiveness of the ions Ca²⁺, Sr²⁺ and Ba²⁺ was shown by use of an ion electrode not to be due to the unavailability of the ionized species. Procedures are described for obtaining highly reproducible results with the Orion Divalent Cation Electrode. The ineffectiveness of the ions Ca²⁺, Sr²⁺ and Ba²⁺ were also shown not to be due to action as general protoplasmic poisons. The effective ions are distinguished from the ineffective ones by characteristic ranges of ionic radii, coordination number, second ionization potentials, electronegativities and affinity constants. Removal of components of complement from the cells by washing in 0.05 M EDTA, and heating all serum used for 30 minutes at 56°C had no significant effect on the adhesiveness of the PMN. A role for complement, therefore appears largely excluded.