Abstract
The effect of low density lipoprotein (LDL) on the microviscosity of cells has been examined to elucidate whether LDL induces altered microviscosity of cell membrane immediately after binding with LDL receptors. Peripheral blood B lymphocytes from healthy adults were used as a model of cells with LDL receptors, and T lymphocytes as well as lymphocytes from patients with familial hyper cholesterolemia were used as control cells which have much less activity as LDL receptors than B lymphocytes. Microviscosity of cell membrane was determined by fluorescence polarization analysis of the fluorescent hydrocarbon probe, 1, 6-diphenyl-1, 3, 5-hexatriene. Elevation of microviscosity after incubation with LDL at 0°C for 30min was induced only in B lymphocytes, but not in T lymphocytes or familial hypercholesterolemic lymphocytes. In parallel studies, it was shown that the activity of LDL receptor was observed exclusively in B lymphocytes but not in T lymphocytes or familial hypercholesterolemic whole lymphocytes.
It is concluded that binding of LDL to LDL receptors increases the microviscosity of membrane without internalization of LDL into cells. It is suggested that this method can be applied for the evaluation of LDL receptor activity under vaious clinical conditions.
