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

我们以前曾报道，鱼精蛋白本身引起选择性区域血管舒张和肝素增强鱼精蛋白诱导的血管变化通过一氧化氮依赖性机制。而一氧化氮系统不参与鱼精蛋白引起的心肌功能障碍。本研究旨在探讨鱼精蛋白诱导的离体大鼠心肌细胞内钙（[Ca 2 +]i）动态变化与心肌功能障碍的关系。我们还研究了带负电荷的肝素是否改变鱼精蛋白的毒性心肌效应。用Langendorff系统灌流大鼠心脏，以Fura-2/AM作为[Ca ~（2+）]i标记物，鱼精蛋白（20 mg/L）染毒后5 min，心肌耗氧量开始和短暂增加，而左心室dP/dt_（max）、收缩期[Ca ~（2+）]i和舒张期[Ca ~（2+）]i无明显变化。注射鱼精蛋白10 min后，左室dP/dt max降低，收缩期[Ca 2 +]i降低。缓冲液洗脱后，收缩压[Ca 2 +]i 关于我们 然而，LV dP/dt max的降低持续了10 min。在鱼精蛋白暴露前肝素（2000 IU/L）的存在导致LV dP/dt max的有害反应。当肝素和鱼精蛋白同时给药时，鱼精蛋白本身的负性肌力作用减弱。当用肝素冲洗心脏时，[Ca ~（2+）]i瞬时幅度恢复较快，而LV dP/dt max无保护作用，提示鱼精蛋白具有直接的负性肌力作用，这种作用是通过降低[Ca ~（2+）]i介导的。鱼精蛋白还降低肌丝Ca 2+敏感性，这可能导致再灌注后持续的心肌抑制。鱼精蛋白暴露前肝素的存在增强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[Ca 2 +]i动力学的影响最小。鱼精蛋白暴露后肝素的存在增强了[Ca 2 +]i瞬变幅度的恢复。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