Osterman A, Arner A, Malmqvist U
Department of Physiology and Biophysics, Lund University, Sölvegatan, Sweden.
J Muscle Res Cell Motil. 1993 Apr;14(2):186-94. doi: 10.1007/BF00115453.
The effects of 2,3-butanedione monoxime (BDM) were studied in smooth muscle fibres from guinea pig taenia coli. In intact muscle, active force during contractions induced by high-K+ was inhibited by about 10% in 1 mM BDM and by approximately 70% in 10 mM BDM. Intracellular [Ca2+] during contraction, measured with the fura-2 technique, was reduced in the presence of BDM. The reduction in force and [Ca2+] in the presence of 1 and 10 mM BDM could be reproduced by reduction in extracellular Ca2+, suggesting that BDM influences the Ca2+ entry or release. In skinned muscle preparations, BDM decreased the Ca2+ sensitivity of active force. This change could be explained by a decreased level of myosin light chain phosphorylation. In fibres maximally activated by thiophosphorylation, the effect of BDM on force occurred at higher concentrations; 10 mM gave no reduction of force and 60 mM 15% reduction. The maximal shortening velocity (Vmax) and force were unaffected by 30 mM BDM in thiophosphorylated muscle and decreased almost in parallel in Ca(2+)-activated contractions. The present results suggest that BDM inhibits myosin light chain phosphorylation, directly decreases force generation at the crossbridge level and inhibits the Ca2+ translocation in smooth muscle. The effect on force in skinned fibres is observed at higher BDM concentrations than those reported to be required for inhibition of force in striated muscle. The inhibition of force in intact smooth muscle could be explained by an influence on Ca2+ translocation.
研究了2,3-丁二酮单肟（BDM）对豚鼠结肠带平滑肌纤维的影响。在完整肌肉中，高钾诱导收缩期间的主动力在1 mM BDM中被抑制约10%，在10 mM BDM中被抑制约70%。用fura-2技术测量的收缩期间细胞内[Ca2+]在BDM存在时降低。在1和10 mM BDM存在下，力和[Ca2+]的降低可通过细胞外Ca2+的减少来重现，表明BDM影响Ca2+的进入或释放。在脱膜肌肉制剂中，BDM降低了主动力的Ca2+敏感性。这种变化可以用肌球蛋白轻链磷酸化水平的降低来解释。在通过硫代磷酸化最大程度激活的纤维中，BDM对力的作用在更高浓度下出现；10 mM时力无降低，60 mM时降低15%。在硫代磷酸化肌肉中，30 mM BDM对最大缩短速度（Vmax）和力无影响，而在Ca(2+)激活的收缩中，二者几乎平行降低。目前的结果表明，BDM抑制肌球蛋白轻链磷酸化，直接降低横桥水平的力产生，并抑制平滑肌中的Ca2+转运。在脱膜纤维中观察到对力的影响时所需的BDM浓度高于报道的横纹肌中抑制力所需的浓度。完整平滑肌中力的抑制可以用对Ca2+转运的影响来解释。
