Radiation-induced changes in permeability in unilamellar phospholipid liposomes.
Gamma-radiation-induced oxidative damage in unilamellar dipalmitoylphosphatidylcholine liposomes was investigated using a fluorescence technique. Liposomal changes in permeability induced by gamma radiation were monitored by measuring the leakage of pre-encapsulated 6-carboxyfluorescein, and alterations in lipid bilayer fluidity were determined by 1,6-diphenyl-1,3,5-hexatriene fluorescence polarization. The changes in permeability and fluidity in the bilayer were found to be dependent on the radiation dose in a biphasic fashion. The results are interpreted in terms of lipid bilayer fluidization after exposure to doses up to 1 kGy, but rigidization of the bilayer at higher doses. These results indicate a relationship between alterations in permeability and fluidity in the lipid bilayer after irradiation. The vesicles were protected significantly against radiation-induced oxidative damage in the presence of alpha-tocopherol and ascorbic acid. Radiation-induced changes in the permeability of the liposomes after exposure to gamma radiation and their modification by antioxidants indicate the involvement of a free radical mechanism in the production of damage, which may offer new insights in to the modification of cellular radiosensitivity by modulation of membrane damage.
Marathe
Dipti
D
Radiation Biology Division, Bhabha Atomic Research Centre, Mumbai-400 085, India.
Mishra
K P
KP
D015060:1,2-Dipalmitoylphosphatidylcholine / Q000378:metabolism; D004307:Dose-Response Relationship, Radiation; D005452:Fluoresceins / Q000378:metabolism; D005454:Fluorescence Polarization; D008081:Liposomes / Q000737:chemistry / Q000528:radiation effects*; D010539:Permeability / Q000528:radiation effects*; D010743:Phospholipids / Q000378:metabolism*; D013696:Temperature
D005452:Fluoresceins; D008081:Liposomes; D010743:Phospholipids; D015060:1,2-Dipalmitoylphosphatidylcholine; C024098:6-carboxyfluorescein