Rosengren S, Arfors K E, Proctor K G
Pharmacia Experimental Medicine, La Jolla, CA 92037.
Int J Microcirc Clin Exp. 1991 Nov;10(4):345-57.
Previous in vitro studies have shown that adenosine (ADO)-induced inhibition of granulocyte function is near maximal at the sub-micromolar concentrations that would be anticipated in normal tissues. If this mechanism is operative in vivo, then antagonizing ADO receptors should potentiate granulocyte-mediated inflammatory responses. To unmask the putative inhibition, the antagonist, 8-phenyl theophylline (8pTHEO), was continuously suffused over the hamster cheek pouch microcirculation, which was observed with intravital bright field and fluorescence microscopy. As an index of inflammation, macromolecular permeability was measured by determining extravasation of fluorescein isothiocyanate-labelled dextran (MW 150,000). In addition, tissue specimens were fixed and stained with hematoxylin and eosin for histological quantification of intravascular and extravascular granulocytes. The tissue was challenged with a 10-40 min topical application of leukotriene B4 (LTB4, 1.1-4nM) or histamine (0.5 or 10 microM) with and without 8pTHEO, at a concentration (8 microM) that attenuated vasodilation evoked by exogenous ADO. These two inflammatory stimuli were chosen because LTB4 evokes a granulocyte-dependent response in the cheek pouch, while histamine evokes a granulocyte-independent response. 8pTHEO potentiated the dose-related increase caused by LTB4 but had no effect on permeability in baseline conditions or on the response evoked by histamine. In baseline conditions, there were fewer than 500 intravascular granulocytes/mm2 microvessel surface area and fewer than 3000 extravascular granulocytes/cm2 tissue surface area. After LTB4 challenge, there was a 3-4 fold increase in the numbers of extra- and intra-vascular granulocytes compared to baseline, but no dose-related relationship could be detected over the concentration range 1.1-4 nM. With 8pTHEO + 1.1 nM LTB4, the granulocyte accumulation was similar to that with LTB4 alone, but there were significantly more intravascular and extravascular granulocytes in the 8pTHEO after 2.5-4 nM LTB4. In context with previous studies, these results suggest that endogenous ADO exerts a tonic inhibitory influence on granulocytes during LTB4 stimulation and this action can be unmasked with methylxanthines.
先前的体外研究表明，在正常组织中预期会出现的亚微摩尔浓度下，腺苷（ADO）对粒细胞功能的抑制作用接近最大值。如果这种机制在体内起作用，那么拮抗ADO受体应该会增强粒细胞介导的炎症反应。为了揭示这种假定的抑制作用，拮抗剂8-苯基茶碱（8pTHEO）持续灌注在仓鼠颊囊微循环上，通过活体明场和荧光显微镜进行观察。作为炎症指标，通过测定异硫氰酸荧光素标记的葡聚糖（分子量150,000）的外渗来测量大分子通透性。此外，将组织标本固定并用苏木精和伊红染色，用于血管内和血管外粒细胞的组织学定量。在有和没有8pTHEO的情况下，用白三烯B4（LTB4，1.1 - 4nM）或组胺（0.5或10μM）局部应用10 - 40分钟对组织进行刺激，8pTHEO的浓度为（8μM），该浓度可减弱外源性ADO引起的血管舒张。选择这两种炎症刺激是因为LTB4在颊囊中引发粒细胞依赖性反应，而组胺引发粒细胞非依赖性反应。8pTHEO增强了LTB4引起的剂量相关的增加，但对基线条件下的通透性或组胺引发的反应没有影响。在基线条件下，每平方毫米微血管表面积的血管内粒细胞少于500个，每平方厘米组织表面积的血管外粒细胞少于3000个。LTB4刺激后，血管内和血管外粒细胞数量比基线增加了3 - 4倍，但在1.1 - 4 nM的浓度范围内未检测到剂量相关关系。使用8pTHEO + 1.1 nM LTB4时，粒细胞聚集与单独使用LTB4时相似，但在2.5 - 4 nM LTB4后，8pTHEO中的血管内和血管外粒细胞明显更多。结合先前的研究，这些结果表明内源性ADO在LTB4刺激期间对粒细胞发挥了强直性抑制作用，并且这种作用可以用甲基黄嘌呤揭示出来。
