REACTION AND DIFFUSION OF NITRIC OXIDE IN BIOLOGICAL SYSTEMS

已有研究表明，一氧化氮(NO)在体内被广泛合成和用作信使分子，但它也具有细胞毒性和诱变作用，是癌症的潜在原因。尽管NO在生物学上具有重要意义，但关于体内或细胞培养系统中NO浓度的空间或时间变化的信息仍然非常有限。对于亚硝酸酐和过氧亚硝酸盐等活性中间体来说更是如此，这些中间体可能是由于局部过量生产NO而对健康造成不利影响的媒介。在大多数感兴趣的条件下测量这些化合物的浓度在技术上是不可行的，但需要这些信息来将细胞培养中测量的毒性水平和突变率与实际暴露水平相关联，并将这些发现与人体的病理情况进行推断。因此，将开发数学模型来预测水溶液、细胞培养物和组织中NO和相关化合物的浓度。因为不同的浓度是由反应和扩散速度之间的竞争决定的，所以模型将基于反应动力学和控制通过水、跨细胞膜和细胞内扩散的物理性质。NO和相关化合物的扩散和反应将在细胞或细胞样颗粒的悬浮液中进行检查，重点是细胞膜的脂质双层成分的通透性和/或反应性。反应扩散模型的预测将在细胞培养系统中得到验证。特别令人感兴趣的是产生大量一氧化氮的细胞和作为其毒性或诱变效应靶标的细胞之间的相互作用。将开发在细胞培养中控制过氧亚硝酸盐输送的方法。其目的是通过化学和物理手段(即不需要“产生”细胞)为“靶细胞”提供已知的、接近生理剂量的过氧亚硝酸根。

It has been shown that nitric oxide (NO) is widely synthesized and used as a messenger molecule in the body, but that it also has cytotoxic and mutagenic effects and is a potential cause of cancer. The biological importance of NO notwithstanding, information on the spatial or temporal variations in NO concentrations in the body or in cell culture systems continues to be very limited. This is doubly true for reactive intermediates such as nitrous anhydride and peroxynitrite, which may be mediators of adverse health effects due to the local overproduction of NO. It is not technically feasible to measure the concentrations of these compounds under most conditions of interest, yet such information is needed to correlate levels of toxicity and rates of mutation measured in cell cultures with actual levels of exposure, and to extrapolate those findings to pathological situations in the body. Accordingly, mathematical models will be developed to predict the concentrations of NO and related compounds in aqueous solutions, cell cultures, and tissues. Because the various concentrations are determined by a competition between rates of reaction and diffusion, the models will be based on reaction kinetics and on the physical properties governing diffusion through water, across cell membranes, and within cells. The diffusion and reaction of NO and related compounds will be examined in suspensions of cells or cell-like particles, with an emphasis on the permeability and/or reactivity of the lipid bilayer component of cell membranes. The predictions of the reaction-diffusion models will be tested in cell culture systems. Of particular interest are the interactions between cells which generate large amounts of NO and cells which act as targets for its toxic or mutagenic effects. Methods will be developed for the controlled delivery of peroxynitrite in cell cultures. The objective there is to provide known, near-physiological doses of peroxynitrite for "target" cells by chemical and physical means (i.e., without the need for "generator" cells).