MICROCYSTINS, NATURAL ENVIRONMENTAL TOXINS

微囊藻毒素是由蓝细菌产生的肽类肝毒素， 通常在包括饮用水供应的水体中形成浮渣， 构成环境公共卫生危害。 我们的最终目标是充分解释这种毒性的机制， 一组化合物。 微囊藻毒素绝对是肝脏特异性的，致命的 导致器官结构丧失的剂量（50 - 200微克/千克，ip） 和大量肝出血几小时内死亡 亚急性剂量被证明是非常有效的肿瘤促进剂， 大鼠肝脏恶性病变发生率增加 二乙基亚硝胺 肝细胞是这些毒素的目标 因为这些细胞不像其他细胞， 缩氨酸 因此，有人提出，运输是排他性的决定因素， 微囊藻毒素的器官选择性毒性 为了达到一个完整的 了解微囊藻毒素肝毒性的性质。身份， 运输过程的性质和活动的控制需要 这是本申请的重点。 具体目标是： 目标1. 研究微囊藻毒素在大鼠肝窦内的转运 膜囊泡 这些将用于探测与有毒物质隔离的运输机制。 细胞相互作用 这些实验将确定传送器 在肝细胞的窦极中起作用，可能表明 改变其活性的策略， 毒素 目标二。 利用非洲爪蟾卵母细胞表达系统， 并克隆了大鼠窦状微囊藻毒素转运蛋白。 运输机的性质和结构将由 通过注射大鼠肝RNA在非洲爪蟾卵母细胞中表达， 识别一种单一的mRNA， 了 将有可能更好地定义运输机制， 在分子水平上确定其他异生物质或代谢物 基板为载体。

Microcystins are peptide hepatotoxins produced by cyanobacteria that commonly form a scum in water bodies including potable water supplies, constituting an environmental public health hazard. Our ultimate goal is to fully explain the mechanism of toxicity of this group of compounds. Microcystins are absolutely liver specific, lethal doses (50-200 migiogram/kg ip) causing loss of the structure of the organ and massive hepatic hemorrhage, followed by death within a few hours. Subacute doses were shown to be very potent tumor promoters causing increased incidence of malignant changes in the liver of rats initiated with diethylnitrosamine. Liver cells are the target of these toxins because these cells, unlike others, have the capacity to take up these peptides. It is proposed that transport therefore is the determinant of the exclusive organ selective toxicity of microcystin. In order to reach a full understanding of microcystin hepatotoxicity the nature. the identity(ies), properties and the control of activity of the transport process need to be addressed which is the focus of this application. The specific aims are: Aim 1. To characterize microcystin transport in rat liver sinusoidal membrane vesicles. These will be used to probe the transport mechanism in isolation from toxic cellular interactions. These experiments will define how the transporter functions in the sinusoidal pole of the hepatocyte and possibly suggest strategies for altering its altering its activity and therefore exposure to the toxins. Aim 2. To use the Xenopus laevis oocyte expression system to characterize and clone the rat sinusoidal microcystin transporter. The nature and structure of the transporter will be determined by expressing it in Xenopus laevis oocytes by injection with rat liver RNA, identifying a the single species of mRNA that is the message and sequencing it. It will be possible to better define the mechanism of the transport at the molecular level and determine what other xenobiotics or metabolites are substrates for the carrier.