Effect of nitric oxide on electrolyte transport across the porcine proximal colon.
The effect of nitric oxide (NO) on ion transport in the porcine proximal colon was investigated in slide-stripped epithelia mounted in Ussing chambers. The serosal addition of the NO-donors sodium nitroprusside (SNP, 0.5 mM) or S-nitroso-N-acetylpenicillamine (SNAP, 0.5 mM) induced a steep increase of short-circuit current ( I(sc)). The stimulatory effect of SNP on I(sc) could not be blocked by piroxicam or tetrodotoxin. Potassium channel inhibitors (quinidine, tetraethylammonium or barium) added serosally reduced the SNP- or SNAP-induced increases of I(sc). In chloride-free solutions, the SNP-induced increase of I(sc) was smaller than in chloride-containing solutions. Cl(- )and Na(+) flux measurements demonstrated that SNP diminished Cl(-) and Na(+) net absorption. Pre-treatment with barium was able to block the inhibitory effect of SNP on NaCl net absorption totally. NO effects on paracellular pathways were assessed by measuring flux rates of [(14)C]-D-mannitol. SNP did not change unidirectional D-mannitol flux rates. In conclusion, NO inhibits NaCl net absorption in the proximal colon of pigs by acting directly on the enterocyte. The antiabsorptive (and/or prosecretory) effect of NO depends on a functional basolateral potassium conductance.
Veterinär-Physiologisches Institut, Universität Leipzig, An den Tierkliniken 7, D-04103 Leipzig, Germany. gaebel@rz.uni-leipzig.de
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Gäbel
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Garz
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Ahrens
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Aschenbach
D000818:Animals; D002712:Chlorides / Q000378:metabolism; D003106:Colon / Q000166:cytology / Q000378:metabolism*; D004553:Electric Conductivity; D004573:Electrolytes / Q000378:metabolism*; D004848:Epithelium / Q000378:metabolism; D066298:In Vitro Techniques; D007425:Intracellular Membranes / Q000378:metabolism; D007473:Ion Channels / Q000502:physiology; D017136:Ion Transport / Q000187:drug effects; D008353:Mannitol / Q000493:pharmacokinetics; D009569:Nitric Oxide / Q000494:pharmacology*; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D010539:Permeability; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000502:physiology; D026423:S-Nitroso-N-Acetylpenicillamine / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism; D013552:Swine / Q000378:metabolism*
D002712:Chlorides; D004573:Electrolytes; D007473:Ion Channels; D020030:Nitric Oxide Donors; D015221:Potassium Channels; D009599:Nitroprusside; D009569:Nitric Oxide; D008353:Mannitol; D026423:S-Nitroso-N-Acetylpenicillamine; D012964:Sodium; D011188:Potassium