Ion channels in isolated mouse jejunal crypts.
The patch-clamp technique was used to characterise the ion channels in cells located in the mid region of mouse jejunal crypts. Six different channels were seen. A large outwardly rectified K+ channel (BK) (conductance, g at 0 mV = 92 +/- 6 pS), which was highly selective for K+ [PK+ (1) > PRb+ (0.6) >> PCs+ (0.09) approximately PNa+ (0.07) > PLi+ (0.04)], had a low, voltage-independent open probability (Po) in the on-cell (O/C) configuration and appeared in 66% of the patches. In inside-out (I/O) patches, this channel had a linear current/voltage (I/V) relationship (g = 132 +/- 3 pS), Po was voltage dependent and it was blocked by cytoplasmic Ba2+ (5 mmol/l). An intermediate K+ channel (IK) which was present in 49% of O/C patches, had a linear I/V (g = 38 +/- 3 pS), ran-down in O/C patches, and was not seen in I/O patches. A number of smaller channels (SC) with conductances ranging from 5 to 20 pS were seen in 16% of O/C patches. Also present in the basolateral membrane were a Cl- channel (ICOR) and a nonselective cation channel (NSCC). These channels were only seen in I/O patches. ICOR had an outwardly rectified conductance (g at 0 mV = 36 +/- 2 pS), its Po was independent of voltage and unaffected by variations in cytoplasmic Ca2+ (100 nmol/l to 1 mmol/l) or ATP (0-1 mmol/l). The NSCC had a linear conductance (20 +/- 1 pS), its Po increased with depolarisation and elevation of cytoplasmic [Ca2+] (> or = 10 micromol/l), but was reduced by cytoplasmic ATP. None of the basolateral channels described here were activated by cAMP-dependent secretagogues, although a Cl- conductance was activated. This cAMP-dependent Cl- conductance was distinct from the basolateral Cl- channel and thus is most likely located in the apical membrane.
Butt
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AG
Department of Physiology, School of Medical Sciences, University of Otago, PO Box 913, Dunedin, New Zealand.
Hamilton
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KL
D000818:Animals; D002412:Cations / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D018118:Chloride Channels / Q000187:drug effects / Q000378:metabolism; D066298:In Vitro Techniques; D007473:Ion Channels / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism*; D007583:Jejunum / Q000378:metabolism*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism
D002412:Cations; D018118:Chloride Channels; D007473:Ion Channels; D015221:Potassium Channels