ALTERED LIPID-COMPOSITION AND DIFFERENTIAL CHANGES IN ACTIVITIES OF MEMBRANE-BOUND ENZYMES OF ERYTHROCYTES IN HEPATIC CIRRHOSIS

Lipid composition, fluidity, and Na+,K+-adenosine triphosphatase (ATPa se), Mg2+-ATPase, and acetylcholinesterase (AChE) activities of erythr ocyte membranes were examined in comparison to plasma lipid compositio n and lecithin:cholesterol acyltransferase (LCAT) activities in 39 pat ients with hepatic cirrhosis due to viral hepatitis (Child-Pugh class A, n = 12; class B, n = 13; and class C, n = 14). Plasma LCAT activiti es decreased and the plasma free-cholesterol to phospholipid molar rat io (C/PL) increased with progressive severity of hepatic cirrhosis. C/ PL and fluorescence polarization (inverse of fluidity) of erythrocyte membranes also increased with disease progression (C/PL: 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 +/- 0.0 02). There was a correlation between C/PL and fluorescence polarizatio n of erythrocyte membranes (r = .629, P < .001). Na+,K+-ATPase activit y of erythrocyte membranes did not differ between cirrhotic patients a nd 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. ACh E and Mg2+-ATPase activities correlated inversely with fluorescence po larization (r = -.652, P < .001 and r = -.381, P < .01, respectively). These results suggest that the free-cholesterol content of erythrocyt e membranes increased in parallel with a decrease in plasma LCAT activ ity with progression of severity of hepatic cirrhosis, and that a resu ltant decrease in membrane fluidity affected Mg2+-ATPase and AChE acti vities but not Na+,K+-ATPase activity. These membrane-bound enzyme act ivities may show different dependencies on membrane fluidity. Copyrigh t (C) 1995 by W.B. Saunders Company