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中枢神经系统 (CNS)的定量微透析研究证实了转运体的存在 ,该转运体与多种药物在脑中的分布有关。存在药物转运体的证据包括 :脑液中游离药物浓度低于血浆中相应浓度 ;通过血脑屏障的转运清除率具有饱和性 ;抑制剂对转运有调节作用。另外 ,通过建立模型 ,将观测药物在CNS血浆或血液中的浓度联系起来 ,找到了主动转运过程或载体中介过程存在的证据。本文对“因为脑脊液中药物浓度低的事实而推断出存在主动输出过程”的结论提出了质疑。若化合物极性相对较大 ,跨越血脑屏障的通透性又较小 ,则脑中化合物的低浓度也可能是由脑液的更新所引起的稀释作用造成的。
Quantitative microdialysis studies of the central nervous system (CNS) confirm the presence of transporters that are involved in the distribution of multiple drugs in the brain. Evidence of the presence of drug transporters includes: the free drug concentration in the brain fluid is lower than the corresponding concentration in the plasma; the clearance rate through the blood-brain barrier is saturated; and the inhibitor modulates the transit. In addition, by establishing a model that correlates the concentration of the observed drug in the plasma or blood of the CNS, evidence of the active transport process or the presence of a carrier-mediated process is found. This paper questions the conclusion that “there is an active output process because of the low concentration of drug in cerebrospinal fluid.” If the compounds are relatively polar and have less permeability across the blood-brain barrier, the low concentrations of compounds in the brain may also be due to dilution caused by brain fluid renewal.