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Basic medical endocrinology - part 4

Cytokine có thể thúc đẩy hoặc đối kháng phát triển của viêm, hoặc có thể có một hỗn hợp của các hiệu ứng chuyên nghiệp, và kháng viêm, tùy thuộc vào các tế bào đặc biệt có liên quan. Prostaglandin và leukotrienes được phát hành chủ yếu từ các tế bào và đại thực bào nội mô mạch máu | Adrenal Cortex 139 produced mainly by cells of the hematopoietic and immune systems but can be synthesized and secreted by virtually any cell. Cytokines may promote or antagonize development of inflammation or may have a mixture of pro- and antiinflammatory effects depending on the particular cells involved. Prostaglandins and leukotrienes are released principally from vascular endothelial cells and macrophages but virtually all cell types can produce and release them. They may also produce either pro- or antiinflammatory effects depending on the particular compound formed and the cells on which they act. Histamine and serotonin are released from mast cells and platelets. Enzymes and superoxides released from dead or dying cells or from cells that remove debris by phagocytosis contribute directly and indirectly to the spread of inflammation by activating other mediators e.g. bradykinin and leukocyte attractants that arise from humoral precursors associated with the immune and clotting systems. Glucocorticoids and the Metabolites of Arachidonic Acid Prostaglandins and the closely related leukotrienes are derived from the polyunsaturated essential fatty acid arachidonic acid Figure 13 . Because of their 20-carbon backbone they are also sometimes referred to collectively as eicosanoids. These compounds play a central role in the inflammatory response. They generally act locally on cells in the immediate vicinity of their production including the cells that produced them but some also survive in blood long enough to act on distant tissues. Prostaglandins act directly on blood vessels to cause vasodilation and indirectly increase vascular permeability by potentiating the actions of histamine and bradykinin. Prostaglandins sensitize nerve endings of pain fibers to other mediators of inflammation such as histamine serotonin bradykinin and substance P thereby producing increased sensitivity to touch hyperalgesia . The leukotrienes stimulate production of cytokines and act