ANGIOTENSIN-II AND RELATED PEPTIDES ALTER LIPOSOMAL MEMBRANE FLUIDITY

We investigated the effects of angiotensinogen (Ang), angiotensin I (A ng I), and angiotensin II (Ang II) on the fluidity of phosphatidylchol ine vesicles. Changes in fluidity were assessed by changes in anisotop y values calculated from fluorescence polarization measurements. All t hree compounds produced an increase in membrane fluidity when localize d inside the phosphatidylcholine vesicles. When placed outside the ves icles, Ang II increased bilayer rigidity (decreased fluidity), whereas Ang and Ang I produced no effect. These results suggest the possibili ty that these peptides may alter the fluidity of cell membranes by a d irect action on the phospholipid bilayer, which may in turn interfere with receptor-mediated effects.