Kinetic evidence distinguishing volume-sensitive chloride current from other types in guinea-pig ventricular myocytes.
1. Kinase-mediated chloride currents (ICl) in guinea-pig ventricular myocytes were activated by application of phorbol ester or forskolin, and compared with currents induced by hyposmotic swelling. Swelling-activated current was identified as ICl from changes in reversal potential, outward rectification and conductance when the Cl-gradient was modified. 2. Kinase-stimulated currents were relatively time and voltage independent, whereas hyposmotic swelling-stimulated (hyposmotic-stimulated) currents inactivated during 100 ms pulses to positive potentials. Forskolin stimulated time-independent ICl in myocytes with current unresponsive to hyposmotic superfusion, and superimposed a similar pedestal on time-dependent ICl in swollen myocytes. 3. Less negative holding potentials depressed hyposmotic-stimulated ICl tested at +80 mV; inhibition was half-maximal at -25 mV. Pulses from -80 to +80 mV inactivated up to 75% of ICl along a multi-exponential time course; repolarization elicited inwardly developing tail currents whose time courses suggest complex gating. 4. Hyperpolarizations, after strongly-inactivating depolarizations, triggered reactivating tail currents whose amplitude and configuration were dependent on voltage and Cl-gradients; tails were large and inwardly developing at potentials negative to the calculated Cl-equilibrium potential (ECl), small and outwardly developing at potentials positive to ECl, and time independent near ECl. 5. These results suggest that the volume-sensitive Cl- channels investigated here are distinct from other Cl- channels in guinea-pig ventricular myocytes. However, their voltage-dependent properties strongly resemble those of volume-sensitive Cl- channels in certain epithelial cells.
Shuba
L M
LM
Department of Physiology and Biophysics, Dalhousie University, Halifax, Nova Scotia, Canada.
Ogura
T
T
McDonald
T F
TF
D000818:Animals; D048429:Cell Size / Q000187:drug effects / Q000502:physiology; D018118:Chloride Channels / Q000187:drug effects / Q000378:metabolism*; D005576:Colforsin / Q000494:pharmacology; D004594:Electrophysiology; D006168:Guinea Pigs; D006352:Heart Ventricles / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D066298:In Vitro Techniques; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D007700:Kinetics; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D009994:Osmolar Concentration; D018408:Patch-Clamp Techniques; D011817:Rabbits; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D018118:Chloride Channels; D005576:Colforsin; D013755:Tetradecanoylphorbol Acetate