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Mechanisms of actions of hydrogen sulphide on rat distal colonic epithelium
Author(s) -
Pouokam E,
Diener M
Publication year - 2011
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.2010.01026.x
Subject(s) - chemistry , biophysics , hyperpolarization (physics) , membrane potential , ion transporter , intracellular , epithelial polarity , ussing chamber , apical membrane , stimulation , cytosol , biochemistry , secretion , endocrinology , membrane , biology , enzyme , stereochemistry , nuclear magnetic resonance spectroscopy
BACKGROUND AND PURPOSE The aim of this study was to clarify the mechanisms by which hydrogen sulphide (H 2 S) affects ion secretion across rat distal colonic epithelium. EXPERIMENTAL APPROACH Changes in short‐circuit current induced by the H 2 S‐donor, sodium hydrosulphide (NaHS; 10 mmol·L −1 ), were measured in Ussing chambers after permeabilization of the apical membrane with nystatin. Cytosolic Ca 2+ concentration ([Ca 2+ ] i ) and Ca 2+ in intracellular stores were measured with fluorescent dyes. Changes in mitochondrial membrane potential were estimated with rhodamine 123. KEY RESULTS NaHS had a biphasic effect on overall currents across the basolateral membrane: an initial inhibition followed by a secondary stimulation. Both a scilliroside‐sensitive action on the Na + ‐K + ‐ATPase and modulation of glibenclamide‐sensitive and tetrapentylammonium‐sensitive (i.e. ATP‐sensitive and Ca 2+ ‐dependent) basolateral K + channels were involved in this action. Experiments with rhodamine 123 revealed that NaHS induced a hyperpolarization of the mitochondrial membrane. NaHS evoked a biphasic change in [Ca 2+ ] i , an initial decrease followed by a secondary increase, known to be mediated by the release of stored Ca 2+ . Initial falls in [Ca 2+ ] i were not mediated by a sequestration of Ca 2+ in intracellular Ca 2+ storing organelles, as the Mag‐Fura‐2 signal was unaffected by NaHS. Falls in [Ca 2+ ] i were inhibited by 2′,4′‐dichlorobenzamil, an inhibitor of the Na + ‐Ca 2+ ‐exchanger, and attenuated in Na + ‐free buffer, suggesting a transient stimulation of Ca 2+ outflow by this transporter, directly demonstrated by Mn 2+ quenching experiments. CONCLUSIONS AND IMPLICATIONS ATP‐sensitive and Ca 2+ ‐dependent basolateral K + conductances, the basolateral Na + ‐K + ‐pump as well as Ca 2+ transporters were involved in the action of H 2 S in regulating colonic ion secretion.