Altered lipid composition and differential changes in activities of membrane-bound enzymes of erythrocytes in hepatic cirrhosis

Abstract 

Lipid composition, fluidity, and Na⁺,K⁺—adenosine triphosphatase (ATPase), Mg²⁺-ATPase, and acetylcholinesterase (AChE) activities of erythrocyte membranes were examined in comparison to plasma lipid composition and lecithin:cholesterol acyltransferase (LCAT) activities in 39 patients with hepatic cirrhosis due to viral hepatitis (Child-Pugh class A, n = 12; class B, n = 13; and class C, n = 14). Plasma LCAT activities decreased and the plasma free—cholesterol to phospholipid molar ratio () increased with progressive severity of hepatic cirrhosis. and fluorescence polarization (inverse of fluidity) of erythrocyte membranes also increased with disease progression (: Child-Pugh A, 0.911 ± 0.010; B, 0.941 ± 0.011; C, 0.979 ± 0.028; and normal, 0.798 ± 0.010; fluorescence polarization: Child-Pugh A, 0.348 ± 0.002; B, 0.351 ± 0.002; C, 0.355 ± 0.002; and normal, 0.340 ± 0.002). There was a correlation between and fluorescence polarization of erythrocyte membranes (r = .629, P < .001). Na⁺,K⁺-ATPase activity of erythrocyte membranes did not differ between cirrhotic patients and normal subjects. On the other hand, Mg²⁺-ATPase activity decreased in Child-Pugh C cirrhosis. AChE activity was decreased in Child-Pugh A cirrhosis, and decreased further in Child-Pugh B and C cirrhosis. AChE and Mg²⁺-ATPase activities correlated inversely with fluorescence polarization (r = −.652, P < .001 and r = −.381, P < .01, respectively). These results suggest that the free-cholesterol content of erythrocyte membranes increased in parallel with a decrease in plasma LCAT activity with progression of severity of hepatic cirrhosis, and that a resultant decrease in membrane fluidity affected Mg²⁺-ATPase and AChE activities but not Na⁺,K⁺-ATPase activity. These membrane-bound enzyme activities may show different dependencies on membrane fluidity.

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