title: Palytoxin-induced K+ efflux from ileal longitudinal smooth muscle of the guinea-pig.
abstract: In guinea-pig ileal longitudinal smooth muscle, both palytoxin (PTX) and carbachol (CCh) increased K+ efflux with an EC50 of 1.8 X 10(-10) M and 4.1 X 10(-7) M, respectively. Atropine (10(-6) M) did not inhibit the K+ efflux due to PTX (3 X 10(-9) M), but completely inhibited the efflux due to CCh (10(-5) M). External Ca2+ removal and verapamil (10(-5) M) did not change the PTX-induced K+ efflux, although the CCh-induced K+ efflux was inhibited about 77% and 71%, respectively. PTX-induced K+ efflux was reduced to 31% by a depletion of intracellular Ca2+. Tetraethylammonium (15 mM) inhibited the K+ efflux due to PTX or CCh to 61% or 75%, respectively. The PTX-induced K+ efflux was also inhibited by cymarin (3 X 10(-8) M), ouabain (10(-5) M) and digitoxin (10(-5) M). These results suggest that the PTX-induced K+ efflux is less dependent on Ca2+ influx than that due to CCh. Furthermore, the binding sites for PTX in the ileal muscle of guinea-pig may be Na+, K+-ATPase, as has been suggested in other types of cells.
mesh_terms: D000178:Acrylamides; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D002118:Calcium / Q000502:physiology; D002217:Carbachol / Q000494:pharmacology; D002301:Cardiac Glycosides / Q000494:pharmacology; D003064:Cnidarian Venoms / Q000494:pharmacology*; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects / Q000378:metabolism; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D000095702:Polyether Toxins
chemical_list: D000178:Acrylamides; D001285:Atropine; D002118:Calcium; D002217:Carbachol; D002301:Cardiac Glycosides; D003064:Cnidarian Venoms; D011188:Potassium; D013757:Tetraethylammonium Compounds; C010272:palytoxin; D000095702:Polyether Toxins