Alterations in rat erythrocyte membrane due to hexachlorocyclohexane (technical) exposure

1998 ◽  
Vol 17 (11) ◽  
pp. 638-642 ◽  
Author(s):  
Pankaj Bhalla ◽  
Deepa Agrawal
Keyword(s):  
Membrane Fluidity ◽  
Erythrocyte Membrane ◽  
Osmotic Fragility ◽  
Structure And Function ◽  
Membrane Structure And Function ◽  
Hydrophobic Molecule ◽  
Erythrocyte Membrane Fluidity ◽  
Membrane Bound ◽  
And Function ◽  
Membrane Bound Enzymes

1 Hexachlorocyclohexane (HCH), an organochlorine pesticide having hydrophobic molecule is known to act on membranes. HCH mediated alterations in erythrocyte membrane occur through disorganization of the lipid bilayer. Therefore the changes in erythrocyte membrane fluidity, osmotic fragility and certain membrane bound enzymes were studied. Administration of HCH (technical) to rats at 5 mg/kg, orally, 5 days a week for 1, 2 and 3 months caused marked increase in erythrocyte membrane fluidity, osmotic fragility anddecreaseinlevelsofNa+, K+-ATPase, acetylcholinesterase in erythrocytes and glutathione in blood. 2 These changes indicate that HCH adversely affects membrane structure and function.

Mechanism of increased erythrocyte membrane fluidity during magnesium deficiency in weanling rats

1989 ◽  
Vol 257 (2) ◽  
pp. C270-C276 ◽  
Author(s):  
S. Tongyai ◽  
Y. Rayssiguier ◽  
C. Motta ◽  
E. Gueux ◽  
P. Maurois ◽  
...  
Keyword(s):  
Membrane Fluidity ◽  
Erythrocyte Membrane ◽  
Magnesium Deficiency ◽  
Osmotic Fragility ◽  
Magnesium Content ◽  
Male Rats ◽  
Surface Irregularities ◽  
Erythrocyte Membrane Fluidity ◽  
And Control

The erythrocyte membrane was investigated in weanling male rats pair fed with magnesium-deficient and control diets for 8 days. Fluorescence polarization studies revealed a 15% increase in the fluidity of membranes from deficient rats. A similar increase in the fluidity of liposomes indicated that protein was not involved. The change was associated with decreased osmotic fragility of intact erythrocytes; the cells lost their biconcavity and had a flattened appearance with surface irregularities. Analysis of the membranes showed decreased amounts of magnesium, cholesterol, and sphingomyelin in the deficient group. The reduced ratios of cholesterol to phospholipid and sphingomyelin to phosphatidylcholine were consistent with the increased fluidity. Addition of physiological amounts of magnesium to the medium rigidified membranes incubated in tris(hydroxymethyl)-aminomethane buffer, and this was prevented by the presence of EDTA. Cross-incubation experiments with erythrocyte ghosts and plasma from the two groups of rats showed that magnesium-deficient plasma increased the fluidity of control ghosts and control plasma rigidified ghosts from magnesium-deficient rats. Addition of sufficient magnesium chloride to raise the magnesium content of deficient plasma to normal had no significant effect. These results show that the increased fluidity of the erythrocyte membrane in magnesium deficiency is due to physicochemical exchange with the plasma. Although magnesium can directly influence membrane fluidity, the change during its deficiency in vivo is mainly mediated indirectly via disturbances in lipid metabolism.

scholarly journals Studies on the biosynthesis of tetrahymanol in Tetrahymena pyriformis. The mechanism of inhibition by cholesterol

1974 ◽  
Vol 142 (1) ◽  
pp. 57-64 ◽  
Author(s):  
Alan S. Beedle ◽  
Kenneth A. Munday ◽  
David C. Wilton
Keyword(s):  
Tetrahymena Pyriformis ◽  
Whole Cells ◽  
Assay Medium ◽  
Mechanism Of Inhibition ◽  
Membrane Structure And Function ◽  
Membrane Bound ◽  
Coa Reductase ◽  
And Function ◽  
Membrane Bound Enzymes

Tetrahymanol biosynthesis by the protozoan Tetrahymena pyriformis was progressively inhibited by the inclusion of cholesterol in the growth medium. Studies with labelled precursors of tetrahymanol have established that there are two major sites of inhibition in whole cells. The inhibition at the first site, between acetate and mevalonate, occurred rapidly after addition of cholesterol. The activity of 3-hydroxy-3-methylglutaryl-CoA reductase (EC 1.1.1.34), a predominantly cytosolic enzyme in this organism, was not inhibited in cholesterol-grown cells nor by addition of cholesterol directly to the assay medium. The second major site of inhibition in whole cells is between mevalonate and squalene and this is accompanied by inhibition of the enzyme that converts farnesyl-pyrophosphate into squalene (squalene synthetase). Squalene cyclase is partially inhibited. The conversion of mevalonate into tetrahymanol in vitro was not inhibited by the addition of cholesterol to the assay medium. Tetrahymanol added to the culture medium is taken up by the cells but does not inhibit endogenous biosynthesis. It is suggested that cholesterol inhibits the later stages of tetrahymanol biosynthesis by causing a change in membrane structure and function which alters the activity of membrane-bound enzymes.

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