title: Secretory modulation of basolateral membrane inwardly rectified K(+) channel in guinea pig distal colonic crypts.
abstract: Cell-attached recordings revealed K(+) channel activity in basolateral membranes of guinea pig distal colonic crypts. Inwardly rectified currents were apparent with a pipette solution containing 140 mM K(+). Single-channel conductance (gamma) was 9 pS at the resting membrane potential. Another inward rectifier with gamma of 19 pS was observed occasionally. At a holding potential of -80 mV, gamma was 21 and 41 pS, respectively. Identity as K(+) channels was confirmed after patch excision by changing the bath ion composition. From reversal potentials, relative permeability of Na(+) over K(+) (P(Na)/P(K)) was 0.02 +/- 0.02, with P(Rb)/P(K) = 1.1 and P(Cl)/P(K) < 0.03. Spontaneous open probability (P(o)) of the 9-pS inward rectifier ((gp)K(ir)) was voltage independent in cell-attached patches. Both a low (P(o) = 0.09 +/- 0.01) and a moderate (P(o) = 0.41 +/- 0.01) activity mode were observed. Excision moved (gp)K(ir) to the medium activity mode; P(o) of (gp)K(ir) was independent of bath Ca(2+) activity and bath acidification. Addition of Cl(-) and K(+) secretagogues altered P(o) of (gp)K(ir). Forskolin or carbachol (10 microM) activated the small-conductance (gp)K(ir) in quiescent patches and increased P(o) in low-activity patches. K(+) secretagogues, either epinephrine (5 microM) or prostaglandin E(2) (100 nM), decreased P(o) of (gp)K(ir) in active patches. This (gp)K(ir) may be involved in electrogenic secretion of Cl(minus sign) and K(+) across the colonic epithelium, which requires a large basolateral membrane K(+) conductance during maximal Cl(-) secretion and, presumably, a lower K(+) conductance during primary electrogenic K(+) secretion.
authors.affiliation: Department of Physiology and Biophysics, Wright State University, 3640 Colonel Glenn Highway, Dayton, OH 45435, USA.
authors.forename: Yingjun
authors.initials: Y
authors.lastname: Li
authors.forename: Dan R
authors.initials: DR
authors.lastname: Halm
mesh_terms: D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D002712:Chlorides / Q000378:metabolism*; D018678:Cholinergic Agents / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D003106:Colon / Q000378:metabolism*; D015232:Dinoprostone / Q000494:pharmacology*; D004837:Epinephrine / Q000494:pharmacology; D006168:Guinea Pigs; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000493:pharmacokinetics*; D024661:Potassium Channels, Inwardly Rectifying / Q000378:metabolism*; D012964:Sodium / Q000494:pharmacology; D013566:Sympathomimetics / Q000494:pharmacology
chemical_list: D002712:Chlorides; D018678:Cholinergic Agents; D024661:Potassium Channels, Inwardly Rectifying; D013566:Sympathomimetics; D005576:Colforsin; D002217:Carbachol; D012964:Sodium; D015232:Dinoprostone; D011188:Potassium; D004837:Epinephrine