Activation of membrane outward currents by human low density lipoprotein in mouse peritoneal macrophages

Summary The aim of the present study was to search for electrophysiological effects of human lipoproteins on membrane currents in mouse peritoneal macrophages which had been cultured for 5 to 20 days. Whole-cell currents were recorded by using a voltage-clamp technique.Low density lipoprotein (LDL, 100 g/ml) increased a slowly activating nonspecific cation current (i_so) in the positive potential range to 244 ± 23% of the reference (test potential + 55 mV, n = 13, P < 0.005). Augmentation of current resulted out of a negative shift of the activation curve along the voltage axis (–22 mV) and an increase of maximally available current.Furthermore, LDL increased a rapidly activating outward current (i_fo) at test potentials positive to the potassium equilibrium potential. At +55 mV i_fo-amplitude increasedto 165 ± 14% ofreference (n = 16, P < 0.005). LDL-induced effects on i_fo-current could be mimicked by application of the calcium ionophore A 23187 (1 mol/l) which led to an increase of i_fo-current to 161 ± 25% of the reference (test potential + 55 mV, n = 11, P < 0.005).Acetylated-LDL (100 g/ml, 5–15 min) produced no significant effect on the membrane currents under investigation. Correspondence to U. Borchard at the above address