Release of unsaturated vitamin B12 binding capacity from human granulocytes by the calcium ionophore A23187

The ionophore A23187, in the presence of calcium ions, was capable of eliciting the release of granule-associated unsaturated vitamin B₁₂ binding capacity from human granulocytes. The ionophore-induced extrusion of unsaturated vitamin B₁₂ binding capacity was concentration, time and temperature-dependent. The release was blocked by 2-deoxyglucose and was unaccompanied by cytotoxicity (trypan-blue uptake and lactate dehydrogenase release). The unsaturated vitamin B₁₂ binding capacity release was accompanied by the release of lysozyme, a specific granule marker enzyme.