5-(N,N-Dimethyl)-amiloride to discriminate the Unidirectional electrolyte transports in rat small intestine and proximal colon in vivo.
The effect of dimethyl-amiloride (DMA), a selective Na+/H+ exchange blocker, was studied on electrolyte net fluxes and unidirectional fluxes of Na and Cl at four levels of rat intestine in vivo in basal conditions. DMA was applied intraluminally at concentrations of 10(-4) and 10(-3) M in the model of ligated loops prepared from duodenum, proximal jejunum, distal ileum and ascending colon in fasted Sprague Dawley rats. Two iso-osmotic test solutions were used: (1) hypo-ionic: Na+ 80 mM and (2) iso-ionic: Na+ 148 mM, pH 8.2. 22Na was placed in the loop and 36Cl was given by intravenous route at the beginning of the experiment. Na+/H+ was calculated by two different means, one was based on pH variation following amiloride inhibition of Na influx, the other on the calculation of the passive Na transport. The quantitative evaluation shows that Na/H exchange largely contributes to the electroneutral absorption and luminal pH regulation. The exchanger activity decreases from duodenum, jejunum, ileum and colon where it is completed by K/H exchange to assure low colon luminal pH.
Laboratoire du Système Neuro-Endocrine et Epithélium Intestinal Normal et Néoplasique INSERM 45, Hôpital Edouard Herriot, Lyon, France.
O
O
Grishina
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K
Volant
D
D
Pansu
M
M
Descroix-Vagne
D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002712:Chlorides / Q000493:pharmacokinetics; D003106:Colon / Q000378:metabolism*; D004386:Duodenum / Q000378:metabolism; D004573:Electrolytes / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007082:Ileum / Q000378:metabolism; D007421:Intestine, Small / Q000378:metabolism*; D017136:Ion Transport; D007583:Jejunum / Q000378:metabolism; D008297:Male; D009994:Osmolar Concentration; D051381:Rats; D017207:Rats, Sprague-Dawley; D012964:Sodium / Q000493:pharmacokinetics; D017923:Sodium-Hydrogen Exchangers / Q000037:antagonists & inhibitors / Q000378:metabolism
D002712:Chlorides; D004573:Electrolytes; D017923:Sodium-Hydrogen Exchangers; C039465:5-dimethylamiloride; D000584:Amiloride; D012964:Sodium