HNO increases myofilament sensitivity to calcium in cardiac muscle through targeting thiol / 中国药学杂志

ABSTRACT

OBJECTIVE: To test the effect of 1-nitrosocyclohexyl acetate (NCA), a newly developed nitroxyl (HNO) donor, on myofilaments and its action mechanism for the thiol in tropomyosin. METHODS: Trabeculae were dissected from the right ventricule of rat heart and mounted between a force transducer and a motor arm. The muscles were superfused with K-H solution (pH 7.4) at room temperature. Fura-2 salt was loaded into the trabeculae via electrophoresis, and the sarcomere length was set at 2.2-2.3 μm. Western blotting tested the change of tropomyosin. RESULTS: Twitch force increased in a dose dependent manner in the presence of NCA in the range of 20-100 μmol·L-1. Force increased (P0.05) with different frequencies (0.5-3.0 Hz) with NCA of 20 μmol·L-1 and Ca2+ of 0.5 μmol·L-1. Skinned force increased as compared to the control (P<0.05). The effect of NCA had characteristics of structure uniqueness. A cross-linking band in tropomyosin was seen by Western blotting under non-reducing condition. The thiol reducing agent dithiothreitol (DTT) both prevented and reversed HNO action. CONCLUSION: The donor of HNO, NCA, represents a new class of agents capable of directly sensitizing cardiac myofilaments to Ca2+. Post-translational thiol modification of the key regulatory myofilament protein (i.e. tropomyosin) may underlie the effect of NCA.