Effect of metabolites on contraction characteristics and ATPase activity of skeletal muscle fibers

The results of The above research project are summarized as follows:1. The effect of L(+)-lactate oncontraction characteristics and ATPase activity of single glycerol-extracted muscle fibersprepared from rabbit psoas muscle was studied by simultaneously recording Ca i - D12+ i -activatedisometric tension,muscle fiber stiffness and ATPase activity in the presence and absence of lactate.2. the maximumisometric force and stiffness decreased roughly in alleled by 2-10% with increasing lactateconcentration from 5 to 25mm .3. The pCa-tension and pCa-ATPase activity relations没有改变appreciably in the presence of lactate.4. the tension cost，obtained from the ATPase activity during steady isometric force generation，decreased by about 8% in the presence of 25mm lactate.5. the unloaded in vitro sliding betweenfluorescently labeled actin filaments and myosin decreased by about 10% in the presence of 25mmlactate，6.这些影响indicate that lactate reduces the efficiency，with which chemical energy derived from ATP hydrolysis ins converted into mechanical work。

The results of the above research project are summarized as follows:1. The effect of L(+)-lactate on the contraction characteristics and ATPase activity of single glycerol-extracted muscle fibers prepared from rabbit psoas muscle was studied by simultaneously recording CaィイD12+ィエD1-activated isometric tension, muscle fiber stiffness and ATPase activity in the presence and absence of lactate.2. The maximum isometric force and stiffness decreased roughly in paralleled by 2-10% with increasing lactate concentration from 5 to 25 mM.3. The pCa-tension and pCa-ATPase activity relations did not change appreciably in the presence of lactate.4. The tension cost, obtained from the ATPase activity during steady isometric force generation, decreased by about 8% in the presence of 25 mM lactate.5. The unloaded in vitro sliding between fluorescently labeled actin filaments and myosin decreased by about 10% in the presence of 25 mM lactate,6. These results indicate that lactate reduces the efficiency, with which chemical energy derived from ATP hydrolysis ins converted into mechanical work.