Photoelectric signals generated by bovine rod outer segment disk membranes attached to a lecithin bilayer.
Purified bovine rod outer segment disk membranes were attached to a lecithin bilayer membrane. After photoexcitation with a 500-nm flash delivered by a dye laser, a negative photovoltage was observed on the bilayer under normal ionic strengths (100 mM KCl), which had a rise phase of 1-3 ms at 20 degrees C. The photoresponse was obviously due to bleaching of rhodopsin as it decreased for successive flashes of light. It originated most probably during the metarhodopsin-I metarhodopsin-II (meta-I-II) transition of rhodopsin because it was pH dependent at 2 degrees C but not at 20 degrees C. At 10 mM KCl, i.e., under hypotonic conditions, a positive photovoltage with slower kinetics than at high salt was observed. As the disk membranes were merely attached to the bilayer membrane, the photovoltage was apparently due to a light-induced transmembrane potential change in the disk membranes. Possible electrogenic mechanisms underlying the photosignal will be discussed.
D000818:Animals; D002417:Cattle; D002462:Cell Membrane / Q000502:physiology; D003080:Cold Temperature; D004594:Electrophysiology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008051:Lipid Bilayers / Q000378:metabolism*; D010713:Phosphatidylcholines; D010777:Photochemistry; D010786:Photoreceptor Cells / Q000502:physiology*; D011189:Potassium Chloride / Q000494:pharmacology; D012243:Rhodopsin / Q000378:metabolism; D012374:Rod Cell Outer Segment / Q000502:physiology*
D008051:Lipid Bilayers; D010713:Phosphatidylcholines; D011189:Potassium Chloride; D012243:Rhodopsin