Effects of MgADP on length dependence of tension generation in skinned rat cardiac muscle.

N. Fukuda*, H. Kajiwara, S. Ishiwata, S. Kurihara

*この研究の対応する著者

研究成果: Article査読

65 被引用数 (Scopus)

抄録

The effect of MgADP on the sarcomere length (SL) dependence of tension generation was investigated using skinned rat ventricular trabeculae. Increasing SL from 1.9 to 2.3 microm decreased the muscle width by approximately 11% and shifted the midpoint of the pCa-tension relationship (pCa(50)) leftward by about 0.2 pCa units. MgADP (0.1, 1, and 5 mmol/L) augmented maximal and submaximal Ca(2+)-activated tension and concomitantly diminished the SL-dependent shift of pCa(50) in a concentration-dependent manner. In contrast, pimobendan, a Ca(2+) sensitizer, which promotes Ca(2+) binding to troponin C (TnC), exhibited no effect on the SL-dependent shift of pCa(50), suggesting that TnC does not participate in the modulation of SL-dependent tension generation by MgADP. At a SL of 1. 9 microm, osmotic compression, produced by 5% wt/vol dextran (molecular weight approximately 464 000), reduced the muscle width by approximately 13% and shifted pCa(50) leftward to a similar degree as that observed when increasing SL to 2.3 microm. This favors the idea that a decrease in the interfilament lattice spacing is the primary mechanism for SL-dependent tension generation. MgADP (5 mmol/L) markedly attenuated the dextran-induced shift of pCa(50), and the degree of attenuation was similar to that observed in a study of varying SL. The actomyosin-ADP complex (AM.ADP) induced by exogenous MgADP has been reported to cooperatively promote myosin attachment to the thin filament. We hereby conclude that the increase in the number of force-generating crossbridges on a decrease in the lattice spacing is masked by the cooperative effect of AM.ADP, resulting in depressed SL-dependent tension generation.

本文言語English
ジャーナルCirculation Research
86
1
出版ステータスPublished - 2000 1月 7
外部発表はい

ASJC Scopus subject areas

  • 生理学
  • 循環器および心血管医学

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