[Effect of human plasma lipoproteins on ionic conductivity of lipid bilayer membranes]

An interaction was studied between various lipoproteins (low density lipoproteins--LDL, very low density lipoproteins--LVDL, subfractions of high density lipoproteins--HDL2, HDL3) and artificial bilayer lipid membranes (BLM) produced from oxydized cholesterol. The lipoproteins increased from 100 to 1000-fold the conductivity of BLM for cations Na+, K+, Ca2+, but not for anions. Critical concentrations of the lipoproteins at which their modifying effect was manifested, correlated reciprocally with the size of the lipoprotein particles; they were arranged as follows: VLDL < LDL < HDL2 < HDL3. Decrease in the pH value lowered these critical concentrations. Addition of Ca2+ into the solution decreased the critical concentrations of VLDL and LDL from 2- to 4-fold as well as of HDL2 and HDL3--from 9- to 12-fold. The electrostatic power appears to be important in interaction between the lipoproteins and bilayer lipid membranes.