Action of palytoxin on apical H+/K+-ATPase in rat colon.
Palytoxin stimulated a cation-dependent short-circuit current (Isc) in rat distal and proximal colon in a concentration-dependent fashion when applied to the mucosal surface of the tissue. The distal colon exhibited a higher sensitivity to the toxin. The palytoxin-induced Isc was blocked by vanadate but was resistant to ouabain or scilliroside, suggesting the conversion of a vanadate-sensitive H+/K+-ATPase into an electrogenic cation transporter. Cation substitution experiments with basolaterally depolarized tissues suggested an apparent permeability of the palytoxin-induced conductance of Na+>K+>Li+. Immunohistochemical control experiments confirmed the absence of the Na+/K+-ATPase in the apical membrane. Consequently, the pore-forming action of palytoxin is not restricted to Na+/K+-ATPase but is also observed with the colonic H+/K+-ATPase.
Institute for Biochemistry and Endocrinology, Institute for Veterinary Physiology, Justus-Liebig-University Giessen, Germany. Georgios.Scheiner-Bobis@vetmed.uni-giessen.de
Georgios
G
Scheiner-Bobis
Thomas
T
Hübschle
Martin
M
Diener
D000178:Acrylamides / Q000494:pharmacology*; D000818:Animals; D001881:Borates / Q000494:pharmacology; D002018:Bufanolides / Q000494:pharmacology; D002463:Cell Membrane Permeability / Q000187:drug effects*; D003064:Cnidarian Venoms / Q000494:pharmacology*; D003106:Colon / Q000187:drug effects* / Q000201:enzymology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D017506:H(+)-K(+)-Exchanging ATPase / Q000187:drug effects*; D007413:Intestinal Mucosa / Q000187:drug effects / Q000201:enzymology; D007473:Ion Channels / Q000187:drug effects*; D017136:Ion Transport / Q000187:drug effects*; D008094:Lithium / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects*; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D017494:Proton Pumps / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D012964:Sodium / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000032:analysis; D014638:Vanadates / Q000494:pharmacology; D000095702:Polyether Toxins
D000178:Acrylamides; D001881:Borates; D002018:Bufanolides; D003064:Cnidarian Venoms; D004791:Enzyme Inhibitors; D017506:H(+)-K(+)-Exchanging ATPase; D007473:Ion Channels; D008094:Lithium; D010042:Ouabain; D011188:Potassium; D017494:Proton Pumps; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D014638:Vanadates; C022879:scilliroside; C010272:palytoxin; D000095702:Polyether Toxins