Dexamethasone-induced alterations in lipid composition and fluidity of rat proximal-small-intestinal brush-border membranes

Abstract

A series of experiments were conducted to examine the possible effects of subcutaneous administration of the synthetic glucocorticoid dexamethasone (100 micrograms/day per 100 g body wt.) on the lipid fluidity and lipid composition of rat proximal-small-intestinal brush-border membranes. After 4 days of treatment, membranes and their liposomes prepared from treated animals possessed a greater fluidity than did their control (diluent, 0.9% NaCl) counterparts, as assessed by steady-state fluorescence-polarization techniques using several different fluorophores. Examination of the effects of temperature on the anisotropy values of 1,6-diphenylhexa-1,3,5-triene, using Arrhenius plots, moreover, revealed that the mean break-point temperatures of the treated preparations were approx. 3-4 degrees C lower than those of their control-preparation counterparts. Changes in the sphingomyelin/phosphatidylcholine (PC) molar ratio as well as in certain of the fatty acids of the PC fraction of treated membranes, secondary to alterations in membrane PC levels and in lysophosphatidylcholine acyltransferase activities respectively, were also noted after dexamethasone administration. These compositional alterations appeared to be responsible, at least in part, for the differences in fluidity noted between treated and control plasma membranes. These results therefore demonstrate that dexamethasone administration can modulate the lipid fluidity and lipid composition of rat proximal-small-intestinal brush-border membranes.

Dexamethasone influences the lipid fluidity, lipid composition and glycosphingolipid glycosyltransferase activities of rat proximal-small-intestinal Golgi membranes

“…Previous studies (Johnston & Melnykovych, 1980;Boullier et al, 1982;Kapitulnik et al, 1986;Brasitus et al, 1987;Dudeja et al, 1987) have shown that dexamethasone increased the lipid fluidity of plasma membranes or intracellular membranes in various cell types. Thus incubation of HeLa cells with dexamethasone for 24 h was previously found to lower the steady-state fluorescence polarization of DPH in intact HeLa-cell membranes and isolated plasma membranes by Johnston &Melnykovych (1980) andBoullier et al (1982).…”

Endocytosis of cholera toxin by human enterocytes is developmentally regulated

“…Corticosteroids, a documented trophic factor (13), have been known to influence the epithelial structure and function of immature enterocytes through several mechanisms including changes in membrane lipid composition (4). Epithelial function has in turn been modulated by changes in membrane lipids.…”

Corticosteroid effect on Caco-2 cell lipids depends on cell differentiation

“…Furthermore, the epithelial functions have been shown to be modulated by membrane lipids [1]. Following appropriate stimuli such as dietary lipids or glucocorticoids, remodelling of membrane phospholipids lead to changes in activities of membrane transporters [6,7]. In addition, phospholipid metabolism is believed to play a role in the regulation of epithelial Na + transport by aldosterone [8][9][10] and inhibition of phospholipase A 2 or fatty acid metabolism have been shown to prevent the enhancement of Na + transport by aldosterone [11,12].…”