増強されたCa2+) 放出とNa/Ca交換活動が,大縮小した犬の心室筋細胞で:収縮性適応と不動脈形成の潜在的な関連
K R Sipido1, P G Volders, S H de Groot
1Laboratory of Experimental Cardiology, University of Leuven, Belgium. karin.sipido@med.kuleuven.ac.be
Circulation
|October 25, 2000
まとめ
心不全では,ナトリウム・カルシウム交換器の活性が増加すると,心筋の機能が改善されるが,カルシウム過負荷と電気活動の変化による危険な心室不律症のリスクが増加する.
科学分野:
- 心血管生理学 心血管の生理学
- 心臓電気生理学 心臓電気生理学
- 心不全 病理生理学 心不全 病理生理学
背景:
- 静脈動脈不調は,心不全および心縮の患者における突然の心臓死の主な原因です.
- 慢性完全心房閉塞 (CAVB) の犬のモデルでは,双心房高縮と心房不律が示され,細胞メカニズムを研究するための貴重なツールとして機能しています.
- 本研究では,CAVBモデルにおける収縮性適応と不動脈形成におけるカルシウム (Ca2+) ホメオスタシスの役割を調査しています.
研究 の 目的:
- 慢性完全心房閉塞 (CAVB) への収縮性適応時のCa2+ホメオスタシスの変化を調査する.
- これらのCa2+ハンドリングの変化がCAVBモデルにおける心房不律症の発生に寄与するかどうかを判断する.
主な方法:
- CAVBで犬の心臓からミオサイトを酵素で分離する.
- 筋細胞の縮小と細胞内Ca2+処理の評価,サルコプラズマ網膜 (SR) のCa2+含量および放出を含む.
- L型Ca2+チャネルとNa/Ca交換器,そしてNa/Ca交換電流によるCa2+流入の測定.
主要な成果:
- CAVB犬のミオサイトは,より低い刺激周波数で,細胞縮小,SR Ca2+放出,SR Ca2+含有量の増加を示した.
- L型Ca2+チャネルを通るCa2+の流入は変わらない.
- Na/Ca交換器経由での Ca2+ の流入の増加は,SR Ca2+ 負荷に寄与し,より大きな内向きの Na/Ca 交換電流が観察されました. これらの変化は,右心房と比較して左心房でより顕著でした.
結論:
- 強化されたNa/Ca交換活動は,CAVB.における収縮機能の改善に寄与する可能性があります.
- しかし,この増加した活動はまた,Ca2+の過負荷を促進することによって,心拍不全の感受性を高めます.
- それはアクションポテンシャルの延長につながり,自発的なCa2+放出中に心律不振を起こす電流を高め,それによって心室不律を容易にすることができます.
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