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

1987 ◽  
Vol 248 (2) ◽  
pp. 455-461 ◽  
Author(s):  
T A Brasitus ◽  
P K Dudeja ◽  
R Dahiya ◽  
A Halline
Keyword(s):  
Lipid Composition ◽  
Brush Border ◽  
Plasma Membranes ◽  
Subcutaneous Administration ◽  
Break Point ◽  
Molar Ratio ◽  
Brush Border Membranes ◽  
Lipid Fluidity ◽  
Intestinal Brush Border ◽  
Small Intestinal

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.

Protein-lipid interactions in human small intestinal brush-border membranes

1989 ◽  
Vol 257 (5) ◽  
pp. G809-G817
Author(s):  
P. K. Dudeja ◽  
J. M. Harig ◽  
K. Ramaswamy ◽  
T. A. Brasitus
Keyword(s):  
Lipid Composition ◽  
Brush Border ◽  
Gamma Glutamyl Transpeptidase ◽  
Lipid Interactions ◽  
Gamma Glutamyl ◽  
Brush Border Membranes ◽  
Lipid Fluidity ◽  
Intestinal Brush Border ◽  
Small Intestinal ◽  
Glutamyl Transpeptidase

Brush-border membranes prepared from proximal and distal human small intestine were characterized with respect to lipid fluidity, lipid composition, and protein-lipid interactions. Steady-state fluorescence polarization and differential polarized phase fluorometry revealed that the "static" and "dynamic" rotational components of fluidity (assessed by r infinity values of 1,6-diphenyl-1,3,5-hexatriene and r values of 12-anthroylstearate, respectively) were greater in the distal membranes compared with their proximal counterparts. The lipid fluidity of distal brush-border membranes was also greater as measured by excimer/monomer fluorescence ratio intensities of pyrene decanoate. A lower molar ratio of cholesterol/phospholipid in the distal membranes was responsible for these regional fluidity differences. Lipid thermotropic transitions were detected at 26-28 degrees C using 1,6-diphenyl-1,3,5-hexatriene in proximal and distal membranes. Arrhenius plots of p-nitrophenylphosphatase and gamma-glutamyl transpeptidase activities demonstrated breakpoints in the vicinity of the lipid thermotropic transition temperatures (28-30 degrees C), whereas maltase and sucrase yielded a single activity slope over the range of 10-40 degrees C. Moreover, 50 mM benzyl alcohol fluidized proximal brush-border membranes and increased p-nitrophenylphosphatase activity in this membrane. This agent also shifted the phase transition temperature of the membrane and breakpoint temperature of this enzymatic activity from approximately 28 degrees C to 19 degrees C. These findings demonstrate that differences in human small intestinal brush-border membrane lipid fluidity and lipid composition exist between proximal and distal regions of this organ. Furthermore, alterations in fluidity and/or lipid composition modulate p-nitrophenylphosphatase and gamma-glutamyl transpeptidase but not sucrase or maltase activities in these membranes.

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

1988 ◽  
Vol 253 (2) ◽  
pp. 401-408 ◽  
Author(s):  
P K Dudeja ◽  
R Dahiya ◽  
M D Brown ◽  
T A Brasitus
Keyword(s):  
Lipid Composition ◽  
Saturation Index ◽  
Subcutaneous Administration ◽  
Break Point ◽  
Fatty Acyl ◽  
Lipid Fluidity ◽  
Golgi Membranes ◽  
Small Intestinal ◽  
And Control ◽  
Increased Activity

Experiments were performed to examine the effects of subcutaneous administration of the synthetic glucocorticoid dexamethasone (100 micrograms/day per 100 g body wt.) on the lipid fluidity, lipid composition and glycosphingolipid glycosyltransferase activities of rat proximal-small-intestinal Golgi membranes. After 4 days of treatment, Golgi membranes and liposomes prepared from treated rats were found to possess a greater fluidity than their control (diluent or 0.9% NaCl) counterpart, as assessed by steady-state fluorescence-polarization techniques using three different fluorophores. Moreover, analysis of the effects of temperature on the anisotropy values of 1,6-diphenylhexa-1,3,5-triene, using Arrhenius plots, demonstrated that the mean break-point temperatures of treated preparations were 4-5 degrees C lower than those of control preparations. Changes in the fatty acyl saturation index and double-bond index of treated membranes, secondary to alterations in stearic acid, linoleic acid and arachidonic acid, at least in part, appeared to be responsible for the differences in fluidity noted between treated and control Golgi membranes. Concomitant with these fluidity and lipid-compositional alterations, treated membranes possessed higher specific activities of UDP-galactosyl-lactosylceramide galactosyltransferase and CMP-N-acetylneuraminic acid:lactosylceramide sialyltransferase than their control counterparts. Experiments utilizing benzyl alcohol, a known fluidizer, furthermore suggested that the fluidity alteration induced by dexamethasone may be responsible for the increased activity of the former, but not the latter, glycosphingolipid glycosyltransferase.

scholarly journals Enhanced Peptide-Binding Capacities of Small Intestinal Brush Border Membranes in Celiac Disease

1999 ◽  
Vol 46 (6) ◽  
pp. 666-666 ◽  
Author(s):  
Gabriele Bolte ◽  
Werner Seilmeier ◽  
Herbert Wieser ◽  
Kati Holm ◽  
Karin Beuermann ◽  
...  
Keyword(s):  
Celiac Disease ◽  
Brush Border ◽  
Peptide Binding ◽  
Brush Border Membranes ◽  
Intestinal Brush Border ◽  
Small Intestinal
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