High C W, Stull J T
Am J Physiol. 1980 Dec;239(6):H756-64. doi: 10.1152/ajpheart.1980.239.6.H756.
Working perfused rabbit and rat hearts were used to determine whether changes in myosin P-light chain phosphate content could affect cardiac contractility. Control perfused rabbit and rat hearts contained 0.48 +/- 0.02 and 0.61 +/- 0.02 mol phosphate/mol P-light chain, respectively. Perfusion of 1) rabbit hearts with 0.1 microM isoproterenol for 30 s, 2) rabbit or rat hearts with a fivefold increase in perfusate [Ca2+] for 30 s, or 3) rabbit hearts with a threefold increase in [Ca2+] for 5 and 15 min caused significant increases in LV dP/dtmax, but had no effect on P-light chain phosphate content. Perfusion of rabbit hearts with Ca2+-free buffer or buffer containing 22 mM K+ caused complete cessation of contractile activity within 30 s and reduced P-light chain phosphate content to 50 and 70%, respectively, of control values after 30 min. Reperfusion of hearts exposed to 22 mM K+ with control buffer restored LV dP/dtmax to control values within 10 min, whereas P-light chain phosphate content remained at 70% of control value. Thus, changes in cardiac contractile state were not accompanied by changes in the extent of phosphorylation of P-light chain.
使用工作中的灌注兔心和大鼠心脏来确定肌球蛋白P轻链磷酸含量的变化是否会影响心脏收缩力。对照灌注的兔心和大鼠心脏分别含有0.48±0.02和0.61±0.02摩尔磷酸/摩尔P轻链。用以下方法灌注：1）用0.1微摩尔异丙肾上腺素灌注兔心30秒；2）用灌注液中[Ca2+]增加五倍的溶液灌注兔心或大鼠心脏30秒；3）用[Ca2+]增加三倍的溶液灌注兔心5分钟和15分钟，均导致左心室dP/dtmax显著增加，但对P轻链磷酸含量没有影响。用无Ca2+缓冲液或含22毫摩尔K+的缓冲液灌注兔心，30秒内收缩活动完全停止，30分钟后P轻链磷酸含量分别降至对照值的50%和70%。用对照缓冲液对暴露于22毫摩尔K+的心脏进行再灌注，10分钟内左心室dP/dtmax恢复到对照值，而P轻链磷酸含量仍为对照值的70%。因此，心脏收缩状态的变化并未伴随着P轻链磷酸化程度的变化。
