Block of inward rectifying K+ channels (KIR) inhibits bradykinin-induced vasodilatation in human forearm resistance vasculature.
OBJECTIVE
To investigate the possible involvement of inward rectifying K(+) channels (K(IR)) in the response of human resistance vessels to bradykinin in vivo.


RESULTS
Drugs were administered via the brachial artery in healthy male volunteers and forearm blood flow was measured by venous occlusion plethysmography. Inhibition of K(IR) by barium chloride (4 micromol min(-1)) alone or with additional inhibition of Na(+)/K(+) ATPase (ouabain 2.7 micromol min(-1)) reduced responses to bradykinin (30 pmol min(-1)), by 26+/-8.3% and 36+/-7.2%, respectively (each P<0 0.05). Barium with ouabain plus inhibitors of prostaglandin (PG) and nitric oxide synthesis inhibited but did not abolish responses to bradykinin (51+/-2.8% inhibition; P<0.01); norepinephrine (240 pmol min(-1)) caused similar reduction of baseline blood flow, as did this combination of inhibitors, but did not significantly inhibit the response to bradykinin. Barium plus ouabain did not significantly reduce responses to acetylcholine or albuterol.


CONCLUSIONS
A component of the vasodilator response to bradykinin in human forearm vasculature is mediated by K(IR). The possible involvement of inward-rectifying K+ channels (KIR) in the action of bradykinin was investigated by administering drugs via the brachial artery in healthy men. Barium selectively inhibited the forearm blood flow response to bradykinin, indicating that a component of this response is mediated by KIR.
Dwivedi
R
R
Department of Clinical Pharmacology, GKT Division of Cardiovascular Medicine, St Thomas' Hospital, London, United Kingdom.
Saha
S
S
Chowienczyk
P J
PJ
Ritter
J M
JM
D000109:Acetylcholine / Q000494:pharmacology; D000328:Adult; D000420:Albuterol / Q000494:pharmacology; D001916:Brachial Artery; D001920:Bradykinin / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D002122:Calcium Chloride / Q000494:pharmacology; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D004347:Drug Interactions; D005542:Forearm / Q000098:blood supply; D006801:Humans; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000187:drug effects; D009638:Norepinephrine / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D010991:Plethysmography; D026902:Potassium Channel Blockers / Q000494:pharmacology*; D024661:Potassium Channels, Inwardly Rectifying / Q000037:antagonists & inhibitors / Q000502:physiology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects*; D014665:Vasodilator Agents / Q000494:pharmacology; D019323:omega-N-Methylarginine / Q000494:pharmacology
D016861:Cyclooxygenase Inhibitors; D026902:Potassium Channel Blockers; D024661:Potassium Channels, Inwardly Rectifying; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D019323:omega-N-Methylarginine; D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase; D002122:Calcium Chloride; D000109:Acetylcholine; D000420:Albuterol; D001920:Bradykinin; D009638:Norepinephrine; D007213:Indomethacin