BIOCHEMICAL MEDICINE AND METABOLIC BIOLOGY 4, 101-108 (1988) Changes of Erythrocyte Membrane Fluidity Associated with Childhood Obesity: A Molecular Study Using Fluorescence Spectroscopy GIANNA FERRETTI, MARIA DOTTI, EDOARDO BARTOLOTTA,* PIER LUIGI GIORGI,* GIOVANNA CURATOLA, AND ENRICO BERTOLI Institutes of Biochemistry and *Pediatrics, Faculty of Medicine, Via Ranieri, 60131 Ancona, Italy Received December 7, 1987. and in revised form March 28, 1988 Obesity, defined in general as a ponderal increase, is usually associated in adult and pediatric patients with abnormalities of plasma lipid and of lipoprotein metabolism (l-4). At the membrane level changes in receptorial and enzymatic activities have been reported in red blood cells (5,6). These observations are particularly relevant since biosynthetic pathways of membrane components are lacking in erythrocytes (7) and their membrane composition depends on exchange with circulating lipoproteins (8). A causal linkage between modifications of li- poprotein metabolism and erythrocyte abnormalities in obesity has not yet been clearly established. However, such a relationship is supported by experimental evidence in other inborn and acquired pathologies (S-10). In a previous study (1 I), in which the electron spin resonance technique (ESR) was used, we have shown a decrease of fluidity at the surface and in the hydrophobic core of erythrocyte membranes obtained from obese children in the absence of major changes in plasma lipids. Moreover the sensitivity of the molecular or- ganization of the erythrocyte membrane to compositional changes (12,13) led us to advance the working hypothesis that erythrocyte membranes could be used as a model in which general metabolic disorders of lipid metabolism could be reflected and amplified. Therefore we decided to further investigate our model by means of fluorescence spectroscopy, which has been widely used to analyze membrane microviscosity in various physiological and pathological cellular systems (10,14-17). The analysis of fluorescence polarization of 1,6-diphenyl-1,3,5hexatriene (DPH) requires a very small membrane sample when compared with the ESR technique, the method is rapid and sensitive enough to be easily applied for routine purposes. In the present report we have evaluated the use of DPH fluorescence to study erythrocyte membranes in childhood obesity and the results have been discussed in relation to compositional changes of erythrocyte membranes and to modifications of clinical parameters. 101 0885-4505/88 $3.00 Copyright 0 1988 by Academic Press. Inc. All rights of reproduction in any form reserved.