Murphy J K, Livingston F R, Gozal E, Torres M, Forman H J
Cell Biology Group, Childrens Hospital Los Angeles, California.
Am J Respir Cell Mol Biol. 1993 Nov;9(5):505-10. doi: 10.1165/ajrcmb/9.5.505.
Exogenous nucleotides can serve as extracellular factors that cause significant functional changes in numerous cells, including phagocytes. In the current study, addition of ATP, ADP, and ATP gamma S directly stimulated the respiratory burst (superoxide production) by rat alveolar macrophages, whereas adenosine and AMP did not. The relative potency of these nucleotides at saturating concentration was ADP > or = ATP gamma S >> ATP; however, simultaneous addition of maximally stimulatory concentrations of ADP and ATP (100 microM of each) produced an additive effect suggesting involvement of two P2 receptors. Following addition of the nucleotides, an elevation of intracellular Ca2+ ([Ca2+]i) occurred within seconds, followed by a decline within 1 min but with a prolonged elevation above baseline for at least 5 min. Removal of extracellular Ca2+ only slightly attenuated the initial elevation, indicating that adenine nucleotides stimulate the rapid release of intracellular Ca2+ stores. Removal of extracellular Ca2+ also eliminated the sustained elevation in [Ca2+]i and markedly suppressed the respiratory burst. Incubation with verapamil, a Ca2+ channel blocker, also significantly inhibited the respiratory burst stimulated by ATP. These studies demonstrate that adenine nucleotides stimulate a Ca(2+)-dependent respiratory burst by rat alveolar macrophages, probably through purinergic receptors.
外源性核苷酸可作为细胞外因子，在包括吞噬细胞在内的众多细胞中引起显著的功能变化。在本研究中，添加ATP、ADP和ATPγS可直接刺激大鼠肺泡巨噬细胞的呼吸爆发（超氧化物生成），而腺苷和AMP则无此作用。这些核苷酸在饱和浓度下的相对效力为ADP≥ATPγS>>ATP；然而，同时添加最大刺激浓度的ADP和ATP（各100μM）产生相加效应，提示涉及两种P2受体。添加核苷酸后，细胞内Ca2+（[Ca2+]i）在数秒内升高，随后在1分钟内下降，但在基线以上持续升高至少5分钟。去除细胞外Ca2+仅轻微减弱初始升高，表明腺嘌呤核苷酸刺激细胞内Ca2+储存的快速释放。去除细胞外Ca2+也消除了[Ca2+]i的持续升高，并显著抑制呼吸爆发。用Ca2+通道阻滞剂维拉帕米孵育也显著抑制了ATP刺激的呼吸爆发。这些研究表明，腺嘌呤核苷酸可能通过嘌呤能受体刺激大鼠肺泡巨噬细胞的Ca(2+)依赖性呼吸爆发。
