Hypoxic vasorelaxation inhibition by organ culture correlates with loss of Kv channels but not Ca(2+) channels.
We (Thorne GD, Shimizu S, and Paul RJ. Am J Physiol Cell Physiol 281: C24-C32, 2001) have recently shown that organ culture for 24 h specifically inhibits relaxation to acute hypoxia (95% N(2)-5% CO(2)) in the porcine coronary artery. Here we show similar results in the porcine carotid artery and the rat and mouse aorta. In the coronary artery, part of the inability to relax to hypoxia after organ culture is associated with a concomitant loss in ability to reduce intracellular Ca(2+) concentration ([Ca(2+)](i)) during hypoxia (Thorne GD, Shimizu S, and Paul RJ. Am J Physiol Cell Physiol 281: C24-C32, 2001). To elucidate the mechanisms responsible for the loss of relaxation to hypoxia, we investigated changes in K(+) and Ca(2+) channel activity and gene expression that play key roles in [Ca(2+)](i) regulation in vascular smooth muscle (VSM). Reduced mRNA expression of O(2)-sensitive K(+) channels (Kv1.5 and Kv2.1) was shown by reverse transcriptase-polymerase chain reaction in the rat aorta. In contrast, no change in other expressed voltage-gated K(+) channels (Kv1.2 and Kv1.3) or Ca(2+) channel subtypes was found. Modified K(+) channel expression is supported by functional evidence indicating a reduced response to general K(+) channel activation, by pinacidil, and to specific voltage-dependent K(+) (Kv) channel blockade by 4-aminopyridine. In conclusion, organ culture decreases expression of specific Kv channels. These changes are consistent with altered mechanisms of VSM contractility that may be involved in Ca(2+)-dependent pathways of hypoxia-induced vasodilation.
Thorne
George D
GD
Department of Molecular and Cellular Physiology, University of Cincinnati, College of Medicine, Cincinnati, Ohio 45267-0576, USA.
Conforti
Laura
L
Paul
Richard J
RJ
D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism*; D002339:Carotid Arteries / Q000187:drug effects / Q000378:metabolism*; D015687:Cell Hypoxia / Q000502:physiology*; D003331:Coronary Vessels / Q000187:drug effects / Q000378:metabolism; D051668:Delayed Rectifier Potassium Channels; D051663:Kv1.2 Potassium Channel; D051664:Kv1.3 Potassium Channel; D051666:Kv1.5 Potassium Channel; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009924:Organ Culture Techniques; D020110:Pinacidil / Q000494:pharmacology; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D024642:Potassium Channels, Voltage-Gated; D011189:Potassium Chloride / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D051669:Shab Potassium Channels; D013552:Swine; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology*
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D051668:Delayed Rectifier Potassium Channels; C496970:Kcna2 protein, mouse; C496972:Kcna2 protein, rat; C496974:Kcna3 protein, mouse; C496975:Kcna3 protein, rat; C496982:Kcna5 protein, mouse; C496983:Kcna5 protein, rat; C496990:Kcnb1 protein, mouse; C496991:Kcnb1 protein, rat; D051663:Kv1.2 Potassium Channel; D051664:Kv1.3 Potassium Channel; D051666:Kv1.5 Potassium Channel; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D012333:RNA, Messenger; D051669:Shab Potassium Channels; D011189:Potassium Chloride; D020110:Pinacidil; D002118:Calcium