Sodium and chloride transport in the large intestine of potassium-loaded rats.
Increased dietary potassium ("potassium loading") induces several adaptive changes in colonic function, including increased potential-dependent potassium secretion, active potassium secretion, and Na-K-ATPase activity, but does not alter net sodium absorption in vivo. To establish whether potassium loading stimulates active sodium transport, unidirectional, net sodium, and chloride fluxes were determined under voltage-clamp conditions across isolated rat distal colonic mucosa. In normal animals net sodium flux (JNanet), net chloride flux (JClnet) and short-circuit current (Isc) were 6.1 +/- 1.1, 8.4 +/- 1.0, and 0.7 +/- 0.1 mu eq X h-1. cm-2, respectively; potassium loading significantly increased JNanet and Isc by 4.9 +/- 1.4 and 3.5 +/- 0.7 mu eq X h-1 X cm-2, respectively, without changing JClnet. Amiloride (0.1 mM) inhibited the increases in JNanet and Isc produced by potassium loading. In Cl-free Ringer solution in normal animals JNanet was reduced to 0.6 +/- 0.3 mu eq X h-1 X cm-2. Potassium loading produced identical increases in JNanet and Isc, which were also completely inhibited by 0.1 mM amiloride. These studies establish that potassium loading induces amiloride-sensitive electrogenic sodium absorption without affecting electroneutral sodium-chloride absorption.
D000222:Adaptation, Physiological; D000450:Aldosterone / Q000378:metabolism; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001693:Biological Transport, Active; D002712:Chlorides / Q000378:metabolism*; D003106:Colon / Q000378:metabolism*; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
D002712:Chlorides; D007473:Ion Channels; D000450:Aldosterone; D000584:Amiloride; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium