虚血心筋におけるトロポニン—Cの減少

The Decrease of Troponin-C in the Ischemic Myocardium

　虚血に伴う心筋構造タンパク質の変化を検討した報告は少ないので，本研究では冠動脈結紮による心筋構造タンパク質の量的変化を検討した．著者らはラットの左冠動脈を結紮して心筋梗塞モデルを作成し，二次元電気泳動法とピリジン抽出法よりなるわれわれの改良した心筋構造タンパク質定量法を用いて，収縮，調節，細胞骨格タンパク質の分解過程を検討した．

　虚血後20分ではコントロール群と虚血群で構造タンパク質含量に有意差はなかった．60分ではトロポニン—Cを除く構造タンパク質に有意差はなかったが，虚血群でトロポニン—Cが有意に減少していた．180分後にはミオシン軽鎖1を除くすべてのタンパク質が減少していた．トロポニン—Cは調節タンパク質の一つでトロポミオシンの存在下でアクチン—ミオシンの相互作用を抑制する．トロポニン—Cの減少は筋原線維の弛緩を抑制し，ひいては虚血心筋の収縮能を低下させるように思われた．

There are few reports about the change of structural proteins caused by ischemia, so we studied the quantita-tive changes of myocardial structural proteins caused by coronary artery ligation. Making a myocardial infarction model on SD rats by ligating the 'left coro-nary artery, we examined the degradative changes of contractile, regulatory, cytoskeletal proteins, using our modified structural protein estimating method, which consisted of two-dimensional electrophoresis and pyridine extraction.

20 minutes after ligation, there was no significant difference in the structural protein contents between the control and the ischemic group. 60 minutes after, the structural proteins, except for troponin-C, were similar in each group. However, troponin-C had decreased significantly in the ischemic group. 180 minutes after, most of the proteins except for myosin light chain 1 had decreased significantly compared with those in the control group. Troponin-C is one of the Ca regulatory proteins which have the interaction between actin and myosin in the presence of tropomyosin. The decrease of troponin-C seemed to suppress the relaxation of myofilaments, which leads to a decrease of contractility in the ischemic myocardium.