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K+ and Cl‐ currents in enterocytes isolated from guinea‐pig small intestinal villi.
Author(s) -
Sepúlveda F V,
Fargon F,
McNaughton P A
Publication year - 1991
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1991.sp018474
Subject(s) - extracellular , chemistry , tetraethylammonium , reversal potential , biophysics , guinea pig , channel blocker , conductance , membrane potential , patch clamp , voltage clamp , charybdotoxin , depolarization , biochemistry , potassium , endocrinology , calcium , biology , receptor , mathematics , organic chemistry , combinatorics
1. The whole‐cell configuration of the patch‐clamp technique has been used to investigate the conductance properties of villus enterocytes isolated from guinea‐pig small intestinal epithelium. 2. With near physiological ionic gradients inward and outward rectification was observed in the hyperpolarizing and depolarizing voltage domains respectively. 3. Replacement of intra‐ and extracellular K+ with N‐methyl‐D‐glucamine (NMG) eliminated inward rectification but did not alter outward currents. In symmetrical low Cl‐ solutions outward currents were reduced but inward rectification was not affected. Under these conditions increases in extracellular K+ shifted both the current‐voltage relation and the extrapolated reversal potential as expected for a K(+)‐selective current. 4. The inwardly rectifying nature of the K+ current observed here remained unaltered after chelation of internal Mg2+ with ATP or EDTA. 5. Extracellular application of 5 mM‐Ba2+ or 50 micrograms ml‐1 of the venom of the scorpion Leiurus quinquestriatus abolished the inward K+ current, while 5 mM‐extracellular tetraethylammonium (TEA) had little effect. 6. The current remaining in the presence of symmetrical Cl‐ solutions and in the complete absence of K+ rectified outwardly and reversed at 0 mV. The anionic nature of this current was confirmed by replacing Cl‐ with different anions. SCN‐ and Br‐ carried more current than Cl‐, while F‐ and gluconate were less permeant. 7. Anionic currents of villus guinea‐pig enterocytes were not stimulated by cyclic AMP and were strongly and reversibly inhibited by the Cl‐ channel blocker 5‐nitro‐2‐(3‐phenylpropylamino) benzoic acid (NPPB, 10(‐5) M). 8. The inwardly rectifying K+ current described here shares some, but not all, characteristics with others previously described. It is postulated that this conductance might function to couple K+ permeability and the Na(+)‐K+ pump rate in enterocytes. Absorption of chloride may be mediated by the Cl‐ channels.