Aderem A A, Scott W A, Cohn Z A
J Cell Biol. 1984 Oct;99(4 Pt 1):1235-41. doi: 10.1083/jcb.99.4.1235.
Murine peritoneal macrophages cultured in minimal essential medium (alpha-MEM; 118 mM Na+, 5 mM K+) released arachidonic acid (20:4) from phospholipids on encountering a phagocytic stimulus of unopsonized zymosan. In high concentrations of extracellular K+ (118 mM), 3H release from cells prelabeled with [3H]20:4 was inhibited 80% with minimal reduction (18%) in phagocytosis. The inhibitory effect of K+ on 20:4 release was fully reversed on returning cells to medium containing Na+ (118 mM). Preingestion of zymosan particles by macrophages maintained in high K+ medium resulted in cells being "primed" for 20:4 release, which was only effected (without the further addition of particles) by changing the medium to one containing Na+. In contrast, 20:4 release from cells stimulated with the calcium ionophore A23187 was unimpaired by the elevated K+ medium, suggesting no direct effect of high K+ on the phospholipase. Macrophages stimulated with zymosan in alpha-MEM metabolized the released 20:4 to prostacyclin, prostaglandin E2 (PGE2), and leukotriene C (LTC). The smaller quantity of released 20:4 in high K+ medium was recovered as 6-Keto-PGF1 alpha, the breakdown product of prostacyclin, and PGE2. No LTC was synthesized. In high K+, resting (no zymosan) macrophages synthesized hydroxyeicosatetraenoic acids from exogeneously supplied 20:4 in proportions similar to cells maintained in alpha-MEM. These findings and the similarity of products (including LTC) produced by A23187 stimulated cells in alpha-MEM and high K+ medium indicated that the cyclooxygenase and lipoxygenase pathway enzymes were not directly inhibited by high extracellular K+. We conclude that high concentrations of extracellular K+ uncouple phagocytosis of unopsonized zymosan from the induction of the phospholipase responsible for the 20:4 cascade and suggest that the lesion is at the level of signal transduction between the receptor-ligand complex and the phospholipase.
在最低限度基本培养基（α - MEM；118 mM Na⁺，5 mM K⁺）中培养的小鼠腹膜巨噬细胞，在遇到未调理酵母聚糖的吞噬刺激时，会从磷脂中释放花生四烯酸（20:4）。在高浓度细胞外K⁺（118 mM）环境下，预先用[³H]20:4标记的细胞中³H的释放被抑制了80%，而吞噬作用仅有轻微降低（18%）。当将细胞重新置于含有Na⁺（118 mM）的培养基中时，K⁺对20:4释放的抑制作用完全逆转。在高K⁺培养基中培养的巨噬细胞预先摄取酵母聚糖颗粒后，细胞会被“启动”以释放20:4，而这只有在将培养基换成含有Na⁺的培养基时才会发生（无需进一步添加颗粒）。相比之下，用钙离子载体A23187刺激细胞时，高K⁺培养基不会损害20:4的释放，这表明高K⁺对磷脂酶没有直接影响。在α - MEM中用酵母聚糖刺激的巨噬细胞会将释放的20:4代谢为前列环素、前列腺素E2（PGE2）和白三烯C（LTC）。在高K⁺培养基中释放的20:4量较少，会以前列环素的分解产物6 - 酮 - PGF1α和PGE2的形式回收。没有合成LTC。在高K⁺环境下，静息（无酵母聚糖）巨噬细胞会从外源提供的20:4中合成羟基二十碳四烯酸，其比例与在α - MEM中培养的细胞相似。这些发现以及α - MEM和高K⁺培养基中A23187刺激的细胞产生的产物（包括LTC）的相似性表明，环氧合酶和脂氧合酶途径的酶不会被高细胞外K⁺直接抑制。我们得出结论，高浓度的细胞外K⁺使未调理酵母聚糖的吞噬作用与负责20:4级联反应的磷脂酶的诱导解偶联，并表明损伤发生在受体 - 配体复合物与磷脂酶之间的信号转导水平。
