title: Photogeneration of membrane potential hyperpolarization and depolarization in non-excitable cells.
abstract: We monitored femtosecond laser induced membrane potential changes in non-excitable cells using patchclamp analysis. Membrane potential hyperpolarization of HeLa cells was evoked by 780 nm, 80 fs laser pulses focused in the cellular cytoplasm at average powers of 30-60 mW. Simultaneous detection of intracellular Ca2+ concentration and membrane potential revealed coincident photogeneration of Ca2+ waves and membrane potential hyperpolarization. By using non-excitable cells, the cell dynamics are slow enough that we can calculate the membrane potential using the steady-state approximation for ion gradients and permeabilities, as formulated in the GHK equations. The calculations predict hyperpolarization that matches the experimental measurements and indicates that the cellular response to laser irradiation is biological, and occurs via laser triggered Ca2+ which acts on Ca2+ activated K+ channels, causing hyperpolarization. Furthermore, by irradiating the cellular plasma membrane, we observed membrane potential depolarization in combination with a drop in membrane resistance that was consistent with a transient laser-induced membrane perforation. These results entail the first quantitative analysis of location-dependent laser-induced membrane potential modification and will help to clarify cellular biological responses under exposure to high intensity ultrashort laser pulses.
authors.affiliation: Department of Applied Physics, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan. ando@ap.eng.osaka-u.ac.jp
authors.forename: Jun
authors.initials: J
authors.lastname: Ando
authors.forename: Nicholas I
authors.initials: NI
authors.lastname: Smith
authors.forename: Katsumasa
authors.initials: K
authors.lastname: Fujita
authors.forename: Satoshi
authors.initials: S
authors.lastname: Kawata
mesh_terms: D020013:Calcium Signaling / Q000528:radiation effects; D002462:Cell Membrane / Q000528:radiation effects; D003593:Cytoplasm / Q000378:metabolism / Q000528:radiation effects; D017097:Electric Impedance; D006367:HeLa Cells; D006801:Humans; D015640:Ion Channel Gating / Q000528:radiation effects; D007834:Lasers; D008564:Membrane Potentials / Q000528:radiation effects*; D018408:Patch-Clamp Techniques; D024681:Potassium Channels, Calcium-Activated / Q000378:metabolism / Q000528:radiation effects
chemical_list: D024681:Potassium Channels, Calcium-Activated