title: Active K transport across rabbit distal colon: relation to Na absorption and Cl secretion.
abstract: We measured isotopic unidirectional fluxes of K to elucidate the mechanisms of active K transport across the distal colon of the rabbit. Separate pathways for active K absorption and active K secretion were detected using various transport inhibitors and stimulators. The rate and direction of net K transport depend on the activities of these two pathways. K absorption was reduced by orthovanadate (both solutions) or serosal Ba, consistent with ATPase-dependent uptake of K across the apical membrane and exit via a Ba-sensitive basolateral K conductance. K secretion was inhibited by serosal ouabain or mucosal Ba, indicating that K secretion involves basolateral uptake via the Na-K pump and apical exit via a Ba-sensitive K conductance. Active K secretion appears to be electrogenic, since inhibition by ouabain produced equivalent changes in the net K flux and short-circuit current. Addition of bumetanide to the serosal solution or the removal of either Na or Cl from the serosal solution inhibited K secretion; mucosal solution amiloride was without effect. These results indicate that this K secretory process is independent of electrogenic Na absorption but is mechanistically similar to Cl secretory processes. Both epinephrine and prostaglandin E2 (PGE2) stimulate K secretion, but only PGE2 also stimulates Cl secretion. The response to these secretogogues suggests that the mechanisms underlying K and Cl secretion are closely linked but can be regulated independently.
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001464:Barium / Q000494:pharmacology; D001693:Biological Transport, Active / Q000187:drug effects; D002034:Bumetanide / Q000494:pharmacology; D002712:Chlorides / Q000378:metabolism*; D003106:Colon / Q000378:metabolism*; D015232:Dinoprostone; D004837:Epinephrine / Q000494:pharmacology; D005260:Female; D007213:Indomethacin / Q000494:pharmacology; D007408:Intestinal Absorption / Q000187:drug effects; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism*; D011458:Prostaglandins E / Q000494:pharmacology; D011817:Rabbits; D012964:Sodium / Q000378:metabolism*; D014638:Vanadates; D014639:Vanadium / Q000494:pharmacology
chemical_list: D002712:Chlorides; D007473:Ion Channels; D011458:Prostaglandins E; D014639:Vanadium; D002034:Bumetanide; D001464:Barium; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; D014638:Vanadates; D010042:Ouabain; D000584:Amiloride; D012964:Sodium; D015232:Dinoprostone; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D011188:Potassium; D007213:Indomethacin; D004837:Epinephrine