EFFECTS OF PROTAMINE ON MYOCARDIAL FUNCTION AND INIRACELLULAR Ca2+ DYNAMICS IN THE ISOLATED RAT HEARTS

我们以前报道过鱼精蛋白本身引起选择性区域血管舒张，肝素通过一氧化氮依赖机制增强了鱼精蛋白诱导的血管变化。然而，一氧化氮系统不参与鱼精蛋白诱导的心肌功能障碍。本研究旨在评估离体大鼠心脏细胞内钙（[Ca2+]i）动力学与鱼精蛋白诱导的心肌功能障碍的关系。我们还研究了带负电荷的肝素是否会改变鱼精蛋白对心肌的毒性作用。用Langendorff系统灌注大鼠心脏，并加载Fura-2/AM作为[Ca2+]i标记物。在鱼精蛋白（20mg /L）暴露后5min，观察到心肌耗氧量的初始和短暂性增加，而左室dP/dt max，收缩期[Ca2+]i和舒张期[Ca2+]i没有变化。鱼精蛋白后10min，左室dP/dt max降低，收缩期[Ca2+]i降低。用缓冲液冲洗后，收缩压[Ca2+]i…More在2分钟内恢复到基线水平。然而，左室dP/dt max下降持续10分钟。在鱼精蛋白暴露之前存在肝素（2000 IU/L）导致LV dP/dt max的有害反应。同时给予肝素和鱼精蛋白时，鱼精蛋白本身的负性肌力作用减弱。当肝素冲洗心脏时，[Ca2+]i瞬态振幅恢复得更快，而在左室dP/dt max中没有观察到保护性反应。这些结果表明，鱼精蛋白具有直接的负性肌力作用，这是由[Ca2+]i的减少介导的。鱼精蛋白也降低肌丝Ca2+敏感性，这可能导致再灌注后持续的心肌抑制。肝素在鱼精蛋白暴露前的存在增强了鱼精蛋白的负性肌力作用。然而，肝素-鱼精蛋白复合物对心肌功能和[Ca2+]i动力学的影响最小。鱼精蛋白暴露后肝素的存在增强了[Ca2+]i瞬态振幅的恢复。少

We have previously reported that protamine itself caused selective regional vasodilation and that heparin potentiated protamine-induced vascular changes via a nitric oxide dependent mechanism. However, nitric oxide system was not involved in protamine induced myocardial dysfunction. This study was designed to assess the relationship between intracellular calcium ([Ca2+]i) dynamics and myocardial dysfunction induced by protamine in the isolated rat hearts. We have also investigated whether negatively charged heparin changes the toxic myocardial effects of protamine. Rat hearts were perfused with a Langendorff system and loaded with Fura-2/AM, as a [Ca2+]i marker.At 5 min after protamine (20 mg/L) exposure, initial and transient increase in myocardial oxygen consumption was observed, whereas LV dP/dt max, systolic [Ca2+]i and diastolic [Ca2+]i did not change yet. At 10 min after protamine, LV dP/dt max decreased and systolic [Ca2+]i decreased. After washout with buffer, systolic [Ca2+]i … More returned to baseline level within 2 min. However, decrease in LV dP/dt max was sustained for 10 min. The presence of heparin (2000 IU/L) prior to protamine exposure resulted in deleterious responses in LV dP/dt max. When heparin and protamine were administered simultaneously, negative inotropic effect of protamine itself was diminished. When the hearts were washed out with heparin, the amplitude of the [Ca2+]i transient recovered more rapidly, whereas no protective response in LV dP/dt max was observed.These results suggested that protamine has a direct negative inotropic effect, which is mediated by a decrease in [Ca2+]i. Protamine also decreases myofilament Ca2+ sensitivity, which may cause sustained myocardial depression after reperfusion. The presence of heparin before protamine exposure enhances negative inotropic effect of protamine. However, heparin-protamine complex has minimum effects on myocardial function and [Ca2+]i dynamics. The presence of heparin after protamine exposure enhances the recovery of the amplitude of the [Ca2+]i transient. Less