Kinetical analysis of pharmacodynamics based on drug-receptor interactions

1)在分子水平上，心糖苷抑制Na^+，K^+- atp酶，这是一种与钠泵相关的膜结合酶。由于钠泵对于维持大多数可兴奋细胞的正常静息电位是必需的，因此一般认为，至少有一部分数字的毒性是由这种酶抑制作用引起的。这种泵抑制是心脏糖苷正性肌力作用（PIA）的原因还是仅仅是一种平行现象，一直存在争议。通过改变输注速率，对瓦沙因在家兔体内PIA的出现过程进行动力学分析。我们还采用快速过滤的方法检测了瓦沙因与心脏组织匀浆中Na^+，K^+- atp酶的特异性结合。在体内实验中，我们以3h -瓦巴因和dp/dt， max作为PIA的指标，同时测量了瓦巴因的血浆浓度（Cp）和PIA。Cp与PIA之间存在明显的输注速率依赖性。此外，PIA的出现过程与瓦沙因从血浆室转移到外周室的动力学过程相同。这一过程不能用PIA与单一受体有关的假设来解释，它的占领过程是PIA出现的限速步骤。体外结合实验表明，乌沙因与心脏Na^+，K^+- atp酶结合缓慢，并分为高亲和力和低亲和力两种类型。因此，Cp和PIA之间的输注速率依赖关系可以用基于两受体的模型来解释。2)在给药氯硝西泮（0.01 ~ 1.0 mg/kg） 1 h后，采用双标记葡萄糖类似物法，根据清醒小鼠脑区3h -3-0-甲基葡萄糖(M)和14c -2-脱氧葡萄糖(D)的脑分布情况，测定局部脑葡萄糖(G)利用情况。大剂量静脉注射两种化合物（M，D）后，获得血浆（C^M,C^D）和脑区示踪剂的时间活性数据。静脉给药D和M后10 min，皮质的表观分布体积（V^D为D， V^M为M）分别为0.64 0.07 （ml/g脑）和0.33 0.03 （ml/g脑）。氯硝西泮存在时，磷酸化清除率（CL^D=(V^D-V^M)/theta）显著降低（30%），而集总常数（LC；LC=LC，同位素效应）没有变化。氯硝西泮存在时，脑区葡萄糖代谢率（rCMRglc=CL^DXC^G/LC）降低（15%）。因此，使用双标签葡萄糖类似物方法，应该可以清楚地看到苯二氮卓类药物对体内区域脑功能的镇静作用。少

1) At the molecular level, cardiac glycosides inhibit Na^+,K^+-ATPase, a membrane bound enzyme associated with the sodium pump. Since the sodium pump is necessary for maintenance of normal resting potential in most excitable cells, it is generally believed that at least a portion of the toxicity of digitals is caused by this enzyme-inhibiting action. It has been controversial whether this pump inhibition is the cause of positive inotropic action (PIA) of cardiac glycosides or just a parallel phenomenon. We then performed the kinetic analysis of the appearance process of PIA of ouabain in the rabbits by changing infusion rate. We also examined the specific binding of ouabain to Na^+,K^+-ATPase in the cardiac tissue homogenate, using rapid filtration method. In in vivo experiments, we measured the plasma concentration (Cp) and PIA of ouabain simultaneously, using 3H-ouabain and dp/dt, max as an index of PIA. Remarkable infusion rate dependency was found in th relationship between Cp and … More PIA. In addition the appearance process of PIA was kinetically the same as that of ouabain transfer from plasma compartment to peripheral compartment. This process could not be explained by the assumption that PIA is related to the single receptor and its occupation process is the rate limiting step of the appearance of PIA. It was made clear from in vitro binding experiments that the binding of ouabain to cardiac Na^+,K^+-ATPase is slow and classified into two types (high and low affinity). Then it is suggested that infusion rate rate dependet relationship between Cp and PIA may be explained by the model based on the two-receptors.2) Local cerebral glucose (G) utilization was measured, using the double-label glucose analogue method, based on the brain disposition of 3H-3-0-methyl-glucose (M) and 14C-2-deoxy-glucose (D) in the brain region of awake mouse, at 1 hr after i.v. administration of clonazepam (0.01-1.0 mg/kg). After bolus i.v. injection of two compounds (M,D), time activity data of tracers in plasma (C^M,C^D) and regional brain were obtained. For cortex, the apparent volume of distribution (V^D for D, V^M for M), at 10 min after i.v. administration of D and M, were 0.64 0.07 (ml/g brain) and 0.33 0.03 (ml/g brain), respectively. The phosphorylation clearance (CL^D=(V^D-V^M)/theta) significangly decreased (30%) in the presence of clonazepam, whereas the lumped constant (LC;LC=LC , isotope-effect) did not change. The glucose metabolic rate (rCMRglc=CL^DXC^G/LC), in the presence of clonazepam, decreased (15%) in the regional brain. Thus, it should be possible to clearly visualize the sedative effects of benzodiazepine on regional brain function in vivo, using the double-label glucose analogue method. Less