Dose dependences of lipid microviscosity of biological membranes induced by synthetic antioxidant potassium phenosan salt

Abstract

Earlier, we demonstrated for the first time that the natural antioxidant α�tocopherol in a wide concentra� tion range can modify the structure of different lipid regions in the endoplasmic reticulum and plasma membranes of hepatocytes in experiments in vitro (1, 2). Despite the biochemical and functional differences between endoplasmic reticulum and plasma mem� branes, they are characterized by similar polymodal nonlinear dose dependences of the effects of α�toco� pherol on the rigidity of superficial (~8 A) and micro� viscosity of buried (~20 A) lipid bilayer regions. Such patterns are typical for biologically active substances, showing an effect over a wide concentration range, including ultralow doses (1, 2). The polymodality of dose dependences is associated with the statistically significant effects of α�tocopherol in three concentra� tion ranges. It is assumed that three possible mecha� nisms of action may underlie the effect of this com� pound depending on its concentration: insertion into the membrane, interaction with specific binding sites, and the information transfer through the layers of water with special physical and chemical properties (1-3). It is known that the main physicochemical characteristic of antioxidants is their ability to inhibit lipid peroxidation (LPO) both in vitro and in vivo, the regulatory system of which includes the microviscosity of lipids (4). In view of above, a question arises as to what are the common and distinctive features of the effects of nat� ural and synthetic agents at ultralow doses and whether the relationship between the ability of antiox� idants to inhibit LPO and modify the structure of bio� logical membranes is retained when they are used at ultralow doses. To answer this question, we assessed the effect of potassium salt of β�(4 �hydroxy�3,5�diter� tbutylphenyl)�propionic acid (potassium phenosan), a synthetic antioxidant, in a wide concentration range on the lipid microviscosity of EPR and PM of hepato� cytes. The study was performed with 100