Properties and regulation of basolateral K+ channels in rat duodenal crypts.
1. Patch clamp recording techniques were used to study the properties of K+ channels in the basolateral membrane of rat duodenal crypts, and their regulation by Cl(-)-secretory agonists. 2. High conductance (84-99 pS) K+ channels were activated by 0.1 mM dibutyryl cAMP in 50% of cell-attached patches, while 0.1 mM carbachol had no effect on channel activity. High conductance K+ channels were voltage independent, Ca2+ insensitive, blocked by 5 mM Ba2+ or 20 mM tetraethylammonium chloride (TEA), and stimulated by 57% when intracellular pH was increased from 7.4 to 7.8. 3. In contrast, low conductance (19-28 pS) K+ channels were activated by 0.1 mM dibutyryl cAMP in 67% of cell-attached patches, while 0.1 mM carbachol activated channels in 100% of cell-attached patches. Low conductance K+ channels were voltage independent, Ca2+ sensitive and pH insensitive. Unlike the high conductance K+ channels, 5 mM Ba2+ had no effect on the activity of low conductance K+ channels, although 20 mM TEA decreased channel activity by 53%. 4. The results show that the basolateral membrane of rat duodenal crypts possesses two discrete populations of K+ channels that may have important roles in sustaining the small intestinal Cl(-)-secretory responses triggered by a variety of cAMP- and Ca(2+)-mediated agonists.
McNicholas
C M
CM
University of Manchester, Department of Medicine, Hope Hospital, Salford.
Fraser
G
G
Sandle
G I
GI
D000818:Animals; D001464:Barium / Q000494:pharmacology; D003994:Bucladesine / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D004386:Duodenum / Q000378:metabolism*; D004553:Electric Conductivity; D006863:Hydrogen-Ion Concentration; D008297:Male; D008871:Microvilli / Q000378:metabolism; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology
D026902:Potassium Channel Blockers; D015221:Potassium Channels; D013757:Tetraethylammonium Compounds; D001464:Barium; D003994:Bucladesine; D019789:Tetraethylammonium; D002118:Calcium