Enodgenous Regulators of Drug Metabolism

这项建议的主要目的是研究生长激素(GH)调节肝脏细胞色素P450(CYP)亚型的性别二型性表达的机制，这影响了人们对治疗药物性别有效性的担忧。在确定了男性的“间歇性”和女性的“连续的”血浆GH谱中的基本成分后，我们现在建议研究肝细胞区分众多GH信号并将它们的信息传递到细胞核的机制。我们假设，循环中的生长激素谱中的每个细胞外信号激活了一个不同的信号转导途径，负责诱导或抑制每一种异构体。我们建议通过给GH缺失的大鼠输注GH信号和使原代大鼠肝细胞暴露于单独的GH信号来识别不同的信号转导途径，这些信号转导通路介导了GH对细胞色素P450的调节。将进行类似的实验，以确定人肝细胞中GH依赖的CYP亚型以及介导其作用的信号转导途径。在成年大鼠中，肝脏细胞色素P450的表达水平是性别相关的(以及在所研究的所有物种中)，无论如何处理，雄性都不能被诱导表达肝脏中完整的雌性模式，雌性也不能被诱导表达正常的雄性模式。我们建议通过确定性别交叉(男性到女性和女性到男性)肝细胞移植中CYP性别逆转的程度来研究性二态CYP亚型是否永久印记。后续研究将检查生长激素信号转导反应中基于性别的印迹差异。

The broad objective of this proposal is to investigate the mechanisms by which growth hormone (GH) regulates the sexually dimorphic expression of hepatic isoforms of cytochrome P450 (CYP), which impacts on concerns regarding the gender- effectiveness of therapeutic agents. Having identified the basic elements in the masculine "episodic" and feminine "continuous" plasma GH profiles that selectively "signal" the expression of 8 constitutive sex-dependent rat CYPs, we now propose to examine the mechanisms by which the hepatocyte discriminates between the numerous GH signals and transduces their messages to the nucleus. We hypothesize that each extracellular signal in the circulating GH profiles activates a different signal transduction pathway responsible for the induction or suppression of each isoform. We propose to identify the different signal transduction pathways mediating GH regulation of CYPs by both infusing GH-devoid rats and exposing primary rat hepatocytes to individual GH signals known to regulate expression of each CYP isoform. Similar experiments will be conducted to identify GH-dependent CYP isoforms in human hepatocytes and the signal transduction pathways mediating their action. Expression levels of hepatic CYPs are gender-dependent in the adult rat (as well as in every other species examined), and regardless of the treatment, males can not be induced to express the full female pattern of hepatic CYPs nor can females be treated to express normal male patterns. We propose to investigate whether the sexually dimorphic CYP isoforms are permanently imprinted by determining the degree of CYP sex reversal in gender crossed (male to female and female to male) hepatocyte transplants. Follow-up studies will examine gender- based imprinting differences in the signal transduction responses to GH signals.