Divergent calciphoretic properties of negatively charged phospholipids in a two-phase system and in liposomes

The ionophoretic properties of several negatively charged phospholipids for transporting calcium ions in an organic phase and across membranes of lipid vesicles have been studied. The amounts of Ca2+ translocated in the organic phase depend on the lipid type but also on the nature of the hydrocarbon chains. Under our experimental conditions, Ca2+ outflow from liposomes is observable with phosphatidic acid derived from egg yolk (PA) and with bovine brain phosphatidyl serine (PS) while dipalmitoyl phosphatidic acid (DPPA), cardiolipin (CL), phosphatidyl inositol (PI) and phosphatidyl inositol diphosphate (PIP2) remained unactive as calcium ionophores through lipid membranes but active as calcium translocators in an organic phase.