HEPATIC FORMATION AND HANDLING OF DRUG METABOLITES

我们希望检验这样一种假设，即肝脏的形成 代谢物以一种空间分布现象的形式出现： 当地产生的代谢物的逗留时间与当地产生的代谢物不同。 预先形成的代谢物，因为它们的进入点不同 肝脏。出现这些差异是因为生成的输入 代谢物依赖于药物的摄取和代谢，以及形成 来自前体的任何代谢物必须先于代谢物 淘汰赛。消除由以下物质产生的代谢物 前体和预制代谢物将不同，尽管 同一代谢酶的参与(S)和过程 用于跨细胞传输。我们建议开发一种深入的 一种形成一种单一代谢物的药物的理论治疗 而不会被进一步消除(代谢或排泄)， B)进一步消除的单一代谢物，以及c)两个或 通过相互竞争的途径形成更多的代谢物。 在实验上，我们希望研究以下底物和 它们在大鼠肝脏灌流制剂中的代谢产物：a)~3H- 对乙酰氨基酚(A)和~3H-水杨胺及其35S-硫酸盐 偶合物；b)14C-依那普利和~3H-依那普利拉；~H-吗啡和 14C-吗啡葡萄糖醛酸脂；14C-乙酰苯胺及其对烷氧基 类似于14C-A和14C-As；c)~3H-三尖杉醇和~3H-4- 甲基伞形酮及其标记的(35S)-硫酸盐和(14C)-硫酸盐 葡萄糖醛酸苷(在没有和存在硫酸盐抑制剂的情况下，DCNP)， 将用TCL和HPLC法进行分析的化合物。而当 以稳定状态维持单程肝脏灌流 输注未标记药物或预制代谢物(不同 输入浓度水平)，快速注射放射性标记 药物、代谢物和血管参比化合物(~(51)Cr- RBC、125I-白蛋白和32P-磷酸)将用于生产 一组多指标稀释曲线(MID)。各种不同的 一次通过技术(正常、逆行、肝动脉) 灌注和MID将提供潜在的信息 过程：红细胞和蛋白质结合、内流(屏障限制、 限流和载体-或浓缩机制)、外流、 以及药物和代谢物形成的隔离以及 预制代谢物在线性和非线性条件下的行为 非线性条件。理论的发展和 通过实验获得的信息将进一步加深我们的知识 代肝与代肝在肝脏处理上的差异 预制代谢物，并为理解 代间毒理学/药理学差异 药物代谢物的加工。

We wish to test the hypothesis that hepatic formation of metabolites occurs as a distributed-in-space phenomenon: the sojourns of a locally generated metabolite will differ from that of preformed metabolite due to their differing points of entry into the liver. These differences occur because input as generated metabolite depends on drug uptake and metabolism, and formation of any metabolite from a precursor must precede metabolite elimination. The elimination of metabolite generated from precursor and preformed metabolite will differ despite involvement of the same metabolizing enzyme(s) and processes for transfer across cells. We propose to develop an indepth theoretical treatment of a drug that forms a) a single metabolite which in turn is not further eliminated (metabolized or excreted), b) a single metabolite which is further eliminated, and c) two or more metabolites formed by competing pathways. Experimentally, we wish to study the following substrates and their metabolites in the perfused rat liver preparation: a) 3H- acetaminophen (A) and 3H-salicylamide and their 35S-sulfate conjugates; b) 14C-enalapril and 3H-enalaprilat; 3H-morphine and 14C-morphine glucuronide; 14C-acetanilide and its p-alkoxy analogs to 14C-A and 14C-AS; c) 3H-harmol and 3H-4- methylumbelliferone and their labeled (35S)-sulfates and (14C)- glucuronides (in absence and presence of sulfate inhibitor, DCNP), compounds that will be assayed by TCL and HPLC. While maintaining a single pass liver perfusion with steadystate infusions of unlabeled drug or preformed metabolite (varying levels of input concentrations), a rapid injection of radiolabeled drug and metabolite and vascular reference compounds (51Cr- RBC, 125I-albumin, and 32p-phosphate) will be used to produce a set of multiple indicator dilution curves (MID). The various techniques (normal, retrograde, hepatic artery) of oncethrough perfusion and MID will provide information on underlying processes: red cell and protein binding, influx (barrier-limited, flowlimited, and carrier- or concentrative mechanisms), efflux, and sequestration of drug and metabolite formation as well as the behaviour of preformed metabolite under both linear and nonlinear conditions. The theoretical development and the experimentally-acquired information will further our knowledge on the differences in hepatic handling between a generated vs preformed metabolite, and provide a solid basis for understanding the toxicological/pharmacological differences in generation and processing of drug metabolites.