K. Imai et al., Alteration in membrane fluidity of rat liver microsomes and of liposomes by protoporphyrin and its anti-lipidoperoxidative effect, BIOL PHAR B, 23(4), 2000, pp. 415-419
The effect of protoporphyrin (PP) on membrane fluidity was investigated by
electron paramagnetic resonance spectroscopy using doxyl stearate spin prob
es in relation to the anti-lipidperoxidative effect of PP. PP decreased the
membrane fluidity in rat liver microsomes at concentrations above 1 mM and
also in phosphatidylcholine (PC)-cholesterol (Cho) (100:8, a molar basis)
liposomes, The lipid peroxidation stimulated by Fe2+ and L-ascorbic acid in
those membrane preparations was attenuated along with the decrease in memb
rane fluidity by PP, Similar results were also found in Cho-rich PC (100:30
to 100) liposomes having less fluidity. These results suggest that the dec
rease in the membrane fluidity caused by PP may be involved in the antioxid
ative action of PP.