Ketamine Stereoselectively Affects Vasorelaxation Mediated by ATP-sensitive K+Channels in the Rat Aorta

2002 ◽  
Vol 97 (4) ◽  
pp. 882-886 ◽  
Author(s):  
Mayuko Dojo ◽  
Hiroyuki Kinoshita ◽  
Hiroshi Iranami ◽  
Katsutoshi Nakahata ◽  
Yoshiki Kimoto ◽  
...  
Keyword(s):  
Sodium Nitroprusside ◽  
Isometric Force ◽  
Inhibitory Effect ◽  
Rat Aorta ◽  
Nitric Oxide Donor ◽  
K Channel ◽  
K Channels ◽  
Channel Opener ◽  
K Channel Opener ◽  
Isolated Rat

Background The effect of ketamine on vasodilation mediated by adenosine triphosphate (ATP)-sensitive K(+) channels has not been studied. The present study was designed to determine whether ketamine might stereoselectively affect vasorelaxation induced by an ATP-sensitive K(+) channel opener in the isolated rat aorta. Methods Rings of the rat aorta with or without endothelium were suspended for isometric force recording. During contraction to phenylephrine (3 x 10(-7) M), vasorelaxation in response to an ATP-sensitive K(+) channel opener levcromakalim (10(-8) to 10(-5) M) or a nitric oxide donor sodium nitroprusside (10(-10) to 10(-5) M) was obtained. Glibenclamide (10(-5) M), S(+) ketamine (10(-4) M), or ketamine racemate (10(-5) to 10(-4) M) was applied 15 min before addition of phenylephrine. Results Vasorelaxation induced by levcromakalim was completely abolished by an ATP-sensitive K(+) channel antagonist glibenclamide (10(-5) M) in the aorta with or without endothelium. Ketamine racemate (3 x 10(-5) to 10(-4) M) significantly inhibited this vasorelaxation in a concentration-dependent fashion, whereas S(+) ketamine did not affect the relaxation. However, the highest concentration of ketamine racemate and S(+) ketamine used in the present study did not alter vasorelaxation in response to sodium nitroprusside in the aorta without endothelium. Conclusion In the isolated rat aorta, clinically relevant concentrations of ketamine racemate can inhibit relaxation induced by an ATP-sensitive K(+) channel opener, whereas S(+) ketamine did not produce any inhibitory effect on this vasorelaxation. These results suggest that ketamine stereoselectively alters vasodilation ATP-sensitive K(+) channels in the conduit artery.

Mild Alkalinization and Acidification Differentially Modify the Effects of Lidocaine or Mexiletine on Vasorelaxation Mediated by ATP-sensitive K+Channels

2001 ◽  
Vol 95 (1) ◽  
pp. 200-206 ◽  
Author(s):  
Hiroyuki Kinoshita ◽  
Hiroshi Iranami ◽  
Yoshiki Kimoto ◽  
Mayuko Dojo ◽  
Yoshio Hatano
Keyword(s):  
Adenosine Triphosphate ◽  
Isometric Force ◽  
Inhibitory Effect ◽  
Rat Aorta ◽  
Ringer Solution ◽  
K Channel ◽  
K Channels ◽  
Blocking Effects ◽  
Ion Channel Blocking

Background The previous study by the authors showed that the class Ib antiarrhythmic drug lidocaine impairs but mexiletine augments vasorelaxation mediated by adenosine triphosphate-sensitive K+ channels. Lidocaine and mexiletine have different values of the negative logarithm of the drug-proton dissociation constant, indicating that the ion channel-blocking effects of these drugs under different pH levels may vary. However, the role of pH in the effects of lidocaine and mexiletine on vasodilation mediated by K+ channels has not been studied. Therefore, the current study was designed to examine whether the inhibition and augmentation of vasorelaxation in response to an adenosine triphosphate-sensitive K+ channel opener, levcromakalim, by the clinically relevant concentrations of lidocaine or mexiletine are modified by mild alkalinization or acidification in the isolated rat aorta. Methods Rings of the rat aorta without endothelium were suspended for isometric force recording. Three types of modified Krebs-Ringer solutions (pH 7.2, 7.4, and 7.6) were prepared by changing the composition of NaCl and NaHCO3. During contractions in response to phenylephrine (3 x 10(-7) M), relaxations in response to levcromakalim (10(-8) to 10(-5) M) were obtained. Lidocaine (10(-5) to 10(-4) M), mexiletine (10(-5) to 10(-4) M), or glibenclamide (10(-5) M) was applied 15 min before addition of phenylephrine. Results Relaxations in response to levcromakalim, which are abolished by the selective adenosine triphosphate-sensitive K+ channel antagonist glibenclamide (10(-5) M), were not different among the three pH groups. In the normal Krebs-Ringer solution of pH 7.4, lidocaine significantly reduced these relaxations in a concentration-dependent fashion. Alkalinization of pH 7.6 augmented the inhibitory effect of lidocaine on these relaxations, whereas acidification of pH 7.2 substantially abolished this effect. In contrast, mexiletine pH independently augmented relaxations in response to levcromakalim. Glibenclamide (10(-5) M) abolished these relaxations in arteries treated with mexiletine (10(-4) M) in any pH group. Conclusions These results suggest that even under conditions of such mild alkalosis or acidosis, vasorelaxation via adenosine triphosphate-sensitive K+ channels is dependent on pH in the presence of clinically relevant concentrations of lidocaine but not mexiletine.

Role of K+Channels in Augmented Relaxations to Sodium Nitroprusside Induced by Mexiletine in Rat Aortas

2000 ◽  
Vol 92 (3) ◽  
pp. 813-820 ◽  
Author(s):  
Hiroyuki Kinoshita ◽  
Toshizo Ishikawa ◽  
Yoshio Hatano
Keyword(s):  
Nitric Oxide ◽  
Smooth Muscle ◽  
Sodium Nitroprusside ◽  
Guanylate Cyclase ◽  
Nitric Oxide Donor ◽  
Nitric Oxide Donors ◽  
K Channels ◽  
Vasodilator Effect ◽  
Isolated Rat

Background A class Ib antiarrhythmic drug, mexiletine, augments relaxations produced by adenosine triphosphate (ATP) sensitive K+ channel openers in isolated rat aortas, suggesting that it produces changes in the vasodilation mediated by ATP-sensitive K+ channels. Nitric oxide can induce its vasodilator effect via K+ channels, including ATP-sensitive K+ channels, in smooth muscle cells. Effects of mexiletine on arterial relaxations to nitric oxide donors, have not been studied. Therefore, the current study in isolated rat aortas was designed to (1) evaluate whether mexiletine augments relaxation in response to nitric oxide donors, including sodium nitroprusside, and (2) determine the role of K+ channels in mediating effects of mexiletine on such nitric oxide-mediated relaxation. Methods Rings of rat aortas without endothelia were suspended for isometric force recording. Concentration-response curves of sodium nitroprusside (10(-10) to 10(-5) M) and 1-hydroxy-2-oxo-3-(N-methyl-3-aminopropyl)-3-methyl-1-triazene (NOC-7; 10(-9) to 10(-5) M) were obtained in the absence and in the presence of mexiletine, in combination with a soluble guanylate cyclase inhibitor, 1H-[1,2,4]oxadiazolo [4,3,-a]quinoxaline-1-one (ODQ), or inhibitors for ATP-sensitive K+ channels (glibenclamide), inward rectifier K+ channels (BaCl2), delayed rectifier K+ channels (4-aminopyridine), large conductance Ca2+-dependent K+ channels (iberiotoxin), or small conductance Ca2+-dependent K+ channels (apamin). Results Mexiletine (10(-5) or 3 x 10(-5) M) augmented relaxations to sodium nitroprusside and NOC-7. In arteries treated with glibenclamide (10(-5) M), mexiletine (3 x 10(-5) M) did not affect relaxations to nitric oxide donors, whereas mexiletine augmented relaxations to sodium nitroprusside despite the presence of BaCl2 (10(-5) M), 4-aminopyridine (10(-3) M), iberiotoxin (5 x 10(-8) M) and apamin (5 x 10(-8) M). Relaxations to sodium nitroprusside were abolished by ODQ (5 x 10(-6) M), whereas these relaxations were augmented by mexiletine (3 x 10(-5) M) in arteries treated with ODQ (5 x 10(-6) M). Conclusions These results suggest that ATP-sensitive K+ channels in vascular smooth muscle, contribute to the augmented vasodilator effect of a nitric oxide donor, sodium nitroprusside induced by mexiletine, and that the vasodilator effect is produced, at least in part, via the guanylate cyclase-independent mechanism.

scholarly journals Dual action of ZD6169, a novel K+ channel opener, on ATP-sensitive K+ channels in pig urethral myocytes

2001 ◽  
Vol 133 (1) ◽  
pp. 154-164 ◽  
Author(s):  
Noriyoshi Teramoto ◽  
Takakazu Yunoki ◽  
Makoto Takano ◽  
Yoshikazu Yonemitsu ◽  
Ichiro Masaki ◽  
...  
Keyword(s):  
K Channel ◽  
K Channels ◽  
Channel Opener ◽  
Dual Action ◽  
K Channel Opener

Phentolamine Precludes Inhibitory Effect of the K+Channel Opener Pinacidil on Insulin Release

1996 ◽  
Vol 28 (01) ◽  
pp. 20-22
Author(s):  
T. Links ◽  
A. Smit ◽  
T. van Haeften ◽  
W. Reitsma
Keyword(s):  
Insulin Release ◽  
Inhibitory Effect ◽  
K Channel ◽  
Channel Opener ◽  
K Channel Opener

Venoconstriction to endothelin-1 in humans: role of calcium and potassium channels

1993 ◽  
Vol 265 (5) ◽  
pp. H1676-H1681 ◽  
Author(s):  
W. G. Haynes ◽  
D. J. Webb
Keyword(s):  
Human Subjects ◽  
K Channel ◽  
K Channels ◽  
Endothelin 1 ◽  
Channel Opener ◽  
K Channel Opener ◽  
Ca2 Channels

Recent studies in vitro have suggested that there may be an interaction between endothelin-1 and ATP-sensitive K+ channels in vascular smooth muscle. Here we have investigated whether agents acting on membrane Ca2+ and K+ channels modulate endothelin-1-induced venoconstriction in vivo in human subjects. In a series of studies, six healthy subjects received, on separate occasions, local infusions into dorsal hand veins of endothelin-1 coinfused with 1) the ATP-sensitive K+ channel opener, cromakalim; 2) the dihydropyridine Ca2+ antagonist, nicardipine; 3) a control vasodilator, hydralazine; and 4) saline placebo. Endothelin-1 caused local venoconstriction with a maximum reduction in vein size of 66 +/- 4% at 60 min (P = 0.0001 vs. basal). Cromakalim prevented endothelin-1-induced venoconstriction (9 +/- 10% maximum constriction; P = 0.68 vs. basal). By contrast, nicardipine, in a dose sufficient to block depolarization-induced constriction caused by K+ infusion, had only a partial effect on endothelin-1-induced venoconstriction (35 +/- 8% maximum constriction; P = 0.001 vs. basal; P = 0.02 vs. endothelin-1), whereas a 10-fold higher dose of nicardipine had no additional effect and hydralazine had no effect. In further studies, cromakalim, but not nicardipine, reversed endothelin-1-induced venoconstriction. Cromakalim did not prevent constriction induced by norepinephrine. Although calcium entry through dihydropyridine-sensitive Ca2+ channels may account in part for the vasoconstrictor action of endothelin-1 in humans, the abolition of endothelin-1 responses by a K+ channel opener suggests additional mechanisms of action for endothelin-1.

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