title: Regulation of a voltage-dependent, calcium-activated K conductance by cyclic GMP in dissociated flounder enterocytes.
abstract: Enterocytes from the winter flounder (Pseudopleuronectes americanus) were isolated by collagenase digestion and maintained in flounder Ringer's solution. Whole cell currents were studied using the amphotericin-perforated whole-cell patch clamp technique. The mean resting membrane potential and capacitance values or dissociated cells were -45 +/- 7 mV and 5 +/- 0.4 pF, respectively. Enterocytes held at -20 mV and treated with 1 mumol.l-1 ionomycin exhibited outward currents when cells were stepped through a series of voltages from -60 to +110 mV. The reversal potential of this current in flounder Ringer's solution was -55 mV and the voltage at which half-maximal activation occurred was +20 mV. Voltage-dependent inhibition of outward current was observed at +60 mV and above. When cells were bathed in symmetric K Ringer's solution the reversal potential shifted to zero mV and no inhibition of current was observed at voltages between -60 and 140 mV. When the holding potential of the cell was changed from -20 to -80 mV and stepped from -60 to +110 mV, a second [previously characterized, O'Grady et al. (1991)] K current with delayed-rectifier properties was identified. This observation demonstrated that the delayed rectifier K channel and the Ca(2+)-activated K channel described in this study exist in the same cell. Extracellular addition of 2 mmol.l-1 Ba2+ to cells bathed in symmetric K Ringer's solution resulted in nearly complete inhibition of outward current. Charybdotoxin produced only minor effects on this current.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Physiology and Animal Sciences, University of Minnesota, St. Paul 55108.
authors.forename: S M
authors.initials: SM
authors.lastname: O'Grady
authors.forename: K E
authors.initials: KE
authors.lastname: Cooper
authors.forename: J L
authors.initials: JL
authors.lastname: Rae
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology; D006152:Cyclic GMP / Q000031:analogs & derivatives* / Q000494:pharmacology; D004553:Electric Conductivity; D005432:Flounder / Q000378:metabolism*; D066298:In Vitro Techniques; D007413:Intestinal Mucosa / Q000378:metabolism*; D007422:Intestines / Q000166:cytology / Q000187:drug effects; D017136:Ion Transport / Q000187:drug effects; D015759:Ionomycin / Q000494:pharmacology; D008564:Membrane Potentials; D011188:Potassium / Q000378:metabolism*; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism
chemical_list: D026902:Potassium Channel Blockers; D015221:Potassium Channels; C016276:8-bromocyclic GMP; D015759:Ionomycin; D006152:Cyclic GMP; D011188:Potassium; D002118:Calcium