The action of stress hormones on the structure and function of erythrocyte membrane.

The action of a mixture of hormones (cortisol and adrenaline) on erythrocyte membrane during their binding was investigated. Changes in the membrane structure were elucidated by atomic force microscopy; microviscosity of the lipid bilayer and changes in the activity of Na(+),K(+)-ATPase at different concentrations of the hormones in erythrocyte suspension were estimated by the fluorescence method. Cortisol and adrenaline were shown to compete for the binding sites. A hormone that managed to bind nonspecifically to the membrane hindered the binding of another hormone. In a mixture of these hormones, cortisol won a competition for the binding sites; therewith, microviscosity of the membranes increased by 25%, which corresponds to a change in microviscosity produced by the action of cortisol alone. The competitive relationships affected also the Na(+),K(+)-ATPase activity, which was indicated by appearance of the second maximum of enzyme activity. It is assumed that an increase in microviscosity of erythrocyte membrane first raises the Na(+),K(+)-ATPase activity due to a growth of the maximum energy of membrane phonons, and then decreases the activity due to hindering of conformational transitions in the enzyme molecule.

Activation of nucleolar DNA expression in hepatocytes by glucocorticoids and high density lipoproteins.

A novel mechanism of protein biosynthesis regulation in liver under the action of reduced forms of steroid hormones (tetrahydrocortisol) and apolipoprotein A-I (apoA-I) is presented. Kupffer cells play an important role in uptake of the cortisol and high density lipoproteins (HDL) as well as in formation of the active complex, tetrahydrocortisol+apolipoprotein A-I (THC-apoA-I). If macrophages are stimulated by lipopolysaccharides (LPS), these processes enhance dramatically, thus causing parallel activation of nucleolar DNA expression and ribosome formation in hepatocytes. THC-apoA-I complex accelerates protein biosynthesis in primary cultures of hepatocytes, but not in macrophages and endotheliocytes.

General model to describe the structure and dynamic balance between different human serum lipoproteins and its practical application.

BACKGROUND: Many dangerous diseases are associated with changes in the concentration of blood lipoproteins (LPs). Thus a fast and accurate method is needed to determine the composition of lipoprotein fractions in human serum. MATERIAL/METHODS: A comparison of 30 parameters characterizing different LPs in serum from 120 healthy donors and 102 multiple sclerosis patients was carried out using a unique algorithm developed to determine the concentrations of all the main lipids and apolipoproteins in each LP fraction and subfraction. Specially developed computer programs and the small-angle X-ray scattering (SAXS) method were used to analyze the literature and experimental data. RESULTS: A general mathematical model has been developed to describe the structure and equilibrium between various LPs, from high density to chylomicrons. All human serum LPs can be regarded as spherical particles, composed of a lipid hydrophobic spherical core consisting of triglycerides and cholesterol esters, and a hydrophilic shell of free cholesterol, phospholipids and apolipoproteins. We show for the first time that the distribution of components among various LP particles can be described by a system of five basic equations and two additional balance equations. The observed difference between control subjects and MS patients was found to be statistically significant in 23 parameters. CONCLUSIONS: In contrast to traditional methods the new method for analyzing human blood LPs is very simple and relatively quick.