title: Two types of stretch-activated channels coexist in the rabbit corneal epithelial cell.
abstract: Ion channels contribute to the regulation of cellular function through control of the membrane potential and intracellular concentration of various ions. We examined stretch-activated channels in the corneal epithelial cell. Patch clamping was applied to enzymatically dissociated corneal epithelial cells to characterize their stretch-activated ion channels. The plasma membrane was stretched by applying suction to the patch pipette in cell-attached or inside-out patch configuration. The ion selectivity, voltage-dependence, and stretch-dependence were examined. Two kinds of stretch-activated channel events were observed; the previously-reported large conductance (L) channel and a novel small conductance (S) channel. The probability of recording L vs. S channels in the cell-attached configuration was about 2:1. The L channel was potassium selective with single channel conductance (gamma) of about 160 pS under the symmetrical (150 mm K+) solution. The S channel was permeable to Na+ and K+ with gamma of about 20 pS under the same conditions. Both L and S channels showed little activity in the absence of suction applied to the recording pipette. Channel activity was evoked by suction (negative pressure) stronger than -20 mmHg in both channels. The open probability (Po) and the mean current increased in proportion to further applied stretch and did not saturate for applied suction as strong as -80 mmHg, the pressure at which the gigaseal started to break. Thus, two types of stretch-activated channels coexist in corneal epithelial cells; a potassium-selective L channel and non-selective S channel. The contribution of these channels to the membrane potential is discussed.
authors.affiliation: Department of Physiology, Keio University School of Medicine, Tokyo, Japan.
authors.forename: S I
authors.initials: SI
authors.lastname: Watanabe
authors.forename: M
authors.initials: M
authors.lastname: Tanizaki
authors.forename: A
authors.initials: A
authors.lastname: Kaneko
mesh_terms: D000818:Animals; D003315:Cornea / Q000502:physiology*; D004848:Epithelium / Q000502:physiology; D015640:Ion Channel Gating / Q000502:physiology; D007473:Ion Channels / Q000502:physiology*; D008564:Membrane Potentials; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000502:physiology; D011312:Pressure; D011817:Rabbits; D013314:Stress, Mechanical
chemical_list: D007473:Ion Channels; D015221:Potassium Channels