The Establishment And Application Of The Transport Kinetics Model Of Xenobiotics Across Blood-Brain Barrier

In situ brain perfusion technique is a rapid, sensitive and quantifiable physiology-based method for studying the transport into the brain across blood-brain barrier and permits absolute control of perfusate composition. The method has been widely used in pharmacokinetics and toxicokinetics. The in situ method coupled to the capillary depletion method allows separating actual transport into brain parenchyma from endocytosis or simple binding to endothelial cells. The kinetics profile of brain uptake is analyzed and appropriate transport or permeability constants are calculated. It allows examining the BBB uptake of various compounds in order to illustrate passive diffusion or carrier-mediated transport or some other mechanisms. For this purpose in situ brain perfusion technique of our own laboratory was built up. The system contains liquid carrying equipments and tubing accessories which were strictly selected and tested. The details of experiment procedure were set on excellent conditions. It is concluded that the technique provides a stable, well-controlled environment in the cerebral microvasculature of the perfused brain, suitable for examining the more reliable characterization of blood to brain transfer.The methods of p-Dimethylaminobenzaldehyde colorimetry determining the concentrations of hydrazine and monomethylhydrazine in rat brain parenchyma were revalidated. A new HPLC-UV method was built to determine the concentration of thenorphine in rat brain samples. The validation results show that these methods are with good specificity, sensitivity, linearity, precision, accuracy and stability. The capillary depletion method for measurement of the vascular trapping component to total brain uptake suggests that thenorphine is transported rather than bound and endocytosed by the brain capillary endothelium.After the building of the kinetics model of xenobiotics transporting across...