title: Ultraviolet photoalteration of late Na+ current in guinea-pig ventricular myocytes.
abstract: UV irradiation has multiple effects on mammalian cells, including modification of ion channel function. The present study was undertaken to investigate the response of membrane currents in guinea-pig ventricular myocytes to the type A (355, 380 nm) irradiation commonly used in Ca(2+) imaging studies. Myocytes configured for whole-cell voltage clamp were generally held at -80 mV, dialyzed with K(+)-, Na(+)-free pipette solution, and bathed with K(+)-free Tyrode's solution at 22 degrees C. During experiments that lasted for approximately 35 min, UVA irradiation caused a progressive increase in slowly-inactivating inward current elicited by 200-ms depolarizations from -80 to -40 mV, but had little effect on background current or on L-type Ca(2+) current. Trials with depolarized holding potential, Ca(2+) channel blockers, and tetrodotoxin (TTX) established that the current induced by irradiation was late (slowly-inactivating) Na(+) current (I(Na)). The amplitude of the late inward current sensitive to 100 microM: TTX was increased by 3.5-fold after 20-30 min of irradiation. UVA modulation of late I(Na) may (i) interfere with imaging studies, and (ii) provide a paradigm for investigation of intracellular factors likely to influence slow inactivation of cardiac I(Na).
authors.affiliation: Department of Physiology and Biophysics, Dalhousie University, Halifax, Nova Scotia, B3H 4H7 Canada.
authors.forename: C
authors.initials: C
authors.lastname: La
authors.forename: Y
authors.initials: Y
authors.lastname: You
authors.forename: P
authors.initials: P
authors.lastname: Zhabyeyev
authors.forename: D J
authors.initials: DJ
authors.lastname: Pelzer
authors.forename: T F
authors.initials: TF
authors.lastname: McDonald
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D006168:Guinea Pigs; D006352:Heart Ventricles / Q000166:cytology; D007473:Ion Channels / Q000378:metabolism / Q000528:radiation effects*; D017136:Ion Transport / Q000502:physiology / Q000528:radiation effects; D008564:Membrane Potentials / Q000502:physiology / Q000528:radiation effects; D032383:Myocytes, Cardiac / Q000502:physiology / Q000528:radiation effects*; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D014466:Ultraviolet Rays; D016276:Ventricular Function
chemical_list: D007473:Ion Channels; D012964:Sodium; D011188:Potassium