Abstract
The change in fluidity by adding pentoxifylline to erythrocyte membranes was compared with that caused by S-adenosyl-L-methionine (SAM) by the method of electron spin resonance (ESR) spectroscopy. When SAM or pentoxifylline was added externally to the erythrocyte suspension (outside), the fluidity of the membrane bilayer was increased after incubation at 37°C. However, the fluidity change in the inner part of the bilayer was relatively small compared to that in its outer part. These fluidity changes were dependent on the incubation time and the temperature. When the erythrocyte suspension was preincubated overnight at 4°C in the presence of durgs (inside), the fluidity of the inner part of the membrane changed significantly. Nevertheless, that of the outer part of the lipid bilayer was not affected. Such an asymmetric fluidity change in the lipid bilayer was not observed by the addition of other xanthine derivatives such as caffeine, theophylline and theobromine. S-Adenosyl-L-homocysteine suppressed and MgCl
2 enhanced the increase of the membrane fluidity by SAM or pentoxifylline. Furthermore, the effects of SAM and pentoxifylline on erythorocyte deformability were determined by a filtering technique method. In increasing order the additive effects of SAM and pentoxifylline on the erythrocyte filterability were SAM (outside)<pentoxifylline (inside)<pentoxifylline (outside)<SAM (inside). These results suggest that pentoxifylline also affects the membrane fluidity through the enzymatic methylation of phospholipids.
