MECHANISMS OF CUTANEOUS ACTIVE VASODILATION IN HUMANS

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。本项目将确定人体皮肤循环中交感血管收缩和血管扩张控制的递质的身份和功能意义。目的：阐明皮肤活性血管扩张剂系统的作用机制。本项目要验证的一般假设是，人体皮肤循环中的主动热调节血管舒张是由一个涉及乙酰胆碱和神经肽的胆碱能共递质系统介导的。具体目的：1)确定热应激时缓激肽是否参与皮肤活动性血管舒张；2)澄清是否在热应激时一氧化氮水平升高并引起皮肤血管活动性舒张，或者是否在热应激时一氧化氮水平保持不变并作为允许因子起作用；3)确定热应激时皮肤活性血管扩张所需的一氧化氮是由内皮型一氧化氮合酶（eNOS）产生还是由神经元型一氧化氮合酶（nNOS）产生；4)确定热应激时血管活性肠多肽（VIP）在皮肤血管活性扩张中的作用；5)确定热应激时cAMP在皮肤活动性血管扩张中的作用；6)确定热应激时cGMP在皮肤活动性血管扩张中的作用；7)测定囊性纤维化患者皮肤血管舒张对胆碱能传递的依赖程度。研究计划：上述具体目标将通过应用一种新的技术组合来解决：皮内微透析和激光多普勒血流法（LDF）。协议将在人类身上进行。皮内微透析将用于将药物输送到皮肤中。生物可利用的NO浓度将通过NO选择性双相电极测量。微透析部位的血流将同时由LDF测量。测量将在基础（体温正常）和刺激（全身加热）的主动血管扩张系统的活动。通过比较基础和刺激活性以及对照（未治疗）和实验（药物治疗）微透析部位之间的反应，将阐明主动血管舒张的机制。方法：1)真皮内电极将用于测量皮肤间质间隙的生物可利用NO水平。2)真皮内微透析将药物输送到间隙。3)激光多普勒血流仪将用于测量在体温和全身加热时血管舒张机制的药理学操作下的血流反应。4)水灌注服（覆盖除手臂、脚和头部以外的整个身体）将分别用冷水、中性水或温水灌注，达到全身降温、恒温或热疗的效果。5)测点局部温度控制采用电阻式加热器。6)用放置在皮肤表面的相对湿度监测器测量出汗率。临床相关性：交感神经系统引起热疗期间皮肤血流量增加的具体机制仍然是谜。提出的实验解决了关于人类这些机制本质的基本问题。这些研究应阐明使用替代疗法治疗热相关疾病潜在风险人群心血管疾病的机制原理。此外，老年人与热有关的死亡发生率更高。在退伍军人中，老年人的比例是美国人口的两倍。该项目将为大量退伍军人提供相关知识。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This project will determine the identity and functional significance of transmitters from sympathetic vasoconstrictor and vasodilator controls in the human cutaneous circulation. OBJECTIVES: To clarify the mechanisms by which the cutaneous active vasodilator system works. The general hypothesis to be tested by this project is that active thermoregulatory vasodilation in the human cutaneous circulation is mediated by a cholinergic co-transmitter system involving acetylcholine and neuropeptides. SPECIFIC AIMS: 1) determine whether bradykinin is involved in cutaneous active vasodilation during heat stress; 2) clarify whether nitric oxide levels increase and cause cutaneous active vasodilation during heat stress or whether the level of nitric oxide remains constant and functions as a permissive factor during heat stress; 3) determine whether the nitric oxide required for cutaneous active vasodilation during heat stress is produced by endothelial nitric oxide synthase (eNOS) or by neuronal nitric oxide synthase (nNOS); 4) Determine the role of vasoactive intestinal polypeptide (VIP) in cutaneous active vasodilation during heat stress; 5) determine the role of cAMP in cutaneous active vasodilation during heat stress; 6) determine the role of cGMP in cutaneous active vasodilation during heat stress; and 7) determine the degree of dependence of cutaneous vasodilation on cholinergic transmission in cystic fibrosis. RESEARCH PLAN: The foregoing specific aims will be addressed by application of a novel combination of techniques: intradermal microdialysis and laser-Doppler Flowmetry (LDF). Protocols will be conducted in humans. Intradermal microdialysis will be used to deliver pharmacological agents into the skin. Bioavailable NO concentrations will be measured by NO-selective, amphometric electrodes. Blood flow at microdialysis sites will be simultaneously measured by LDF. Measurements will be made during basal (normothermia) and stimulated (whole body heating) activity of the active vasodilator system. By comparing the responses between basal and stimulated activity and between control (untreated) and experimental (drug treated) microdialysis sites, the mechanisms of active vasodilation will be elucidated. METHODS: 1) Intra-dermal electrodes will serve to measure interstitial bioavailable NO levels from the cutaneous interstitial space. 2) Intra-dermal microdialysis will serve to deliver drugs into the interstitial space. 3) Laser-Doppler Flowmetry will be used to measure blood flow responses to pharmacological manipulation of vasodilator mechanisms during normothermia and whole body heating. 4) A water perfused suit (covers the entire body except for arms, feet, and head) will be used to effect whole body cooling, normothermia, or hyperthermia by perfusing with cold, neutral, or warm water respectively. 5) Local temperature control of measurement sites will be accomplished with resistive heaters. 6) Sweat rate is measured with relative humidity monitors placed on the skin surface. CLINICAL RELEVANCE: The specific mechanisms whereby the sympathetic nervous system causes increases in skin blood flow during hyperthermia remain enigmatic. The proposed experiments address fundamental questions about the nature of these mechanisms in humans. These studies should clarify the mechanistic rationale for use of alternative therapies to treat cardiovascular disorders in persons potentially at risk for heat related disorders. In addition, elderly populations have a greater incidence of heat related deaths. Among Veterans, the percentage of elderly is twice that of the U.S. population. This project will provide knowledge relevant to a significant number of veterans.