Photomodification of the electrical properties of the plasma membrane: a comparison between 6 different membrane-active photosensitizers.
The present study deals with photomodification of the electrical properties of the plasma membrane of an epithelial cell line (opossum kidney (OK) cells). The effect of photofrin II (previously investigated) is compared with that of 5 other membrane-active sensitizers: sulfonated Zn-phthalocyanine, merocyanine 540, rose bengal, methylene blue and protoporphyrin IX (an endogenous sensitizer induced by addition of its biosynthetic precursor 5-aminolaevulinic acid). The study was performed in order to investigate whether photomodification of the ion transport properties of the plasma membrane by membrane-active sensitizers is a general and early event in cellular photosensitization. The changes in the electrical properties were monitored by application of the whole-cell and the inside-out configuration of the patch-clamp technique. Illumination in the presence of the compounds (apart from merocyanine 540) gave rise to similar changes of the electrical properties of the membrane: depolarization of the membrane potential, inactivation of a large-conductance, Ca2+-dependent K+-channel (maxi-KCa), and a strong increase of the leak conductance of the membrane. This similarity indicates the general character of the functional photomodifications by membrane-active sensitizers previously reported for photofrin II.
Killig
F
F
Department of Biology, University of Konstanz, Box M638, D-78457 Konstanz, Germany.
Kunz
L
L
Stark
G
G
D000622:Aminolevulinic Acid / Q000494:pharmacology; D000818:Animals; D002460:Cell Line / Q000187:drug effects / Q000528:radiation effects; D002462:Cell Membrane / Q000187:drug effects* / Q000528:radiation effects; D017323:Dihematoporphyrin Ether / Q000494:pharmacology; D004553:Electric Conductivity; D007211:Indoles / Q000494:pharmacology; D017136:Ion Transport / Q000187:drug effects / Q000528:radiation effects; D054833:Isoindoles; D007668:Kidney; D008027:Light; D008564:Membrane Potentials / Q000187:drug effects*; D008751:Methylene Blue / Q000494:pharmacology; D009893:Opossums; D009942:Organometallic Compounds / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010777:Photochemistry; D017319:Photosensitizing Agents / Q000494:pharmacology*; D011524:Protoporphyrins / Q000096:biosynthesis / Q000502:physiology; D011744:Pyrimidinones / Q000494:pharmacology; D012395:Rose Bengal / Q000494:pharmacology; D017967:Zinc Compounds
D007211:Indoles; D054833:Isoindoles; D009942:Organometallic Compounds; D017319:Photosensitizing Agents; D011524:Protoporphyrins; D011744:Pyrimidinones; D017967:Zinc Compounds; C052159:Zn(II)-phthalocyanine; D012395:Rose Bengal; C003954:merocyanine dye; D000622:Aminolevulinic Acid; D017323:Dihematoporphyrin Ether; C028025:protoporphyrin IX; D008751:Methylene Blue