title: Iloprost dilates rat small arteries: role of K(ATP)- and K(Ca)-channel activation by cAMP-dependent protein kinase.
abstract: The effect of the stable prostacyclin analog iloprost and its mechanism of action were investigated with the use of pressurized rat tail small arteries with a spontaneous myogenic tone. Iloprost concentration dependently dilated these vessels with a half-maximal effective dose of 5.0 +/- 0.5 x 10(-8) M. Application of 10(-7)-10(-6) M glibenclamide, a blocker of ATP-sensitive potassium (K(ATP)) channels, inhibited the iloprost-induced dilation. Glibenclamide did not affect the basal vessel diameter. The application of 5 x 10(-5)-10(-3) M tetraethylammonium (TEA) and 5 x 10(-9)-10(-7) M iberiotoxin, blockers of calcium-activated potassium (K(Ca)) channels, decreased vessel diameter in the presence of iloprost. Both TEA and iberiotoxin reduced the basal vessel diameter. Glibenclamide at 10(-6) M inhibited the dilation produced by 5 x 10(-5) M Sp-5,6-DCl-cBIMPS, an activator of adenosine 3',5'-cyclic monophosphate (cAMP)-dependent protein kinase. Iberiotoxin at 10(-7) M decreased vessel diameter in the presence of Sp-5,6-DCl-cBIMPS. H-89 and Rp-8-CPT-cAMPS, blockers of cAMP-dependent protein kinase A (PKA), inhibited the iloprost-induced dilation of these vessels. With use of the whole cell configuration of the patch-clamp technique, it was observed that 5 x 10(-7) M iloprost enhanced an outward current, determined largely by K(Ca) channels, 1.79 +/- 0.17-fold in freshly isolated smooth muscle cells from rat tail small artery. These data show that iloprost dilates rat tail small arteries with a spontaneous myogenic tone and suggest that K(ATP) as well as K(Ca) channels are involved in this effect, which is mediated, at least partly, by PKA.
authors.affiliation: Faculty of Medicine, University of Rostock, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Schubert
authors.forename: V N
authors.initials: VN
authors.lastname: Serebryakov
authors.forename: H
authors.initials: H
authors.lastname: Mewes
authors.forename: H H
authors.initials: HH
authors.lastname: Hopp
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001158:Arteries / Q000187:drug effects / Q000502:physiology*; D002118:Calcium / Q000494:pharmacology; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004004:Dichlororibofuranosylbenzimidazole / Q000031:analogs & derivatives / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005905:Glyburide / Q000494:pharmacology*; D016285:Iloprost / Q000494:pharmacology*; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D010455:Peptides / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D011921:Rats, Inbred WKY; D012604:Scorpion Venoms / Q000494:pharmacology; D013623:Tail / Q000098:blood supply; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology; D013873:Thionucleotides / Q000494:pharmacology; D014661:Vasoconstriction; D014664:Vasodilation / Q000187:drug effects
chemical_list: D004791:Enzyme Inhibitors; D010455:Peptides; D015221:Potassium Channels; D012604:Scorpion Venoms; D013757:Tetraethylammonium Compounds; D013873:Thionucleotides; C071644:5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole-3',5'-monophosphorothioate; C074155:8-chloroadenosine-3',5'-cyclic monophosphorothioate; D004004:Dichlororibofuranosylbenzimidazole; D019789:Tetraethylammonium; C064719:iberiotoxin; D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D016285:Iloprost; D005905:Glyburide; D002118:Calcium