Deliconstantinos G, Kopeikina L, Ramantanis G
Department of Experimental Physiology, University of Athens, Medical School, Greece.
Anticancer Res. 1989 May-Jun;9(3):fluorescence polarization.
PGE2 and PGA2 incubated for 30 min at 25 degrees C with microsomal membranes isolated from Walker-256 tumour, in the presence of 50 microM indomethacin increase the lipid fluidity estimated by steady-state fluorescence anisotropy [(r0/r)-1]-1, using 1,6-diphenyl-1,3,5-hexatriene (DPH) as probe. The microsomal preparations of Walker-256 tumour contained calcium-stimulated and magnesium-dependent ATPase as well as calmoduling-dependent guanylate cyclese activities. A considerable decrease (approx. 65%) in the activity of the Ca2+-stimulated ATPase was observed when preparations were treated with 10 microM PGE2 and PGA2. A dramatic gradual decrease of the calmodulin-dependent guanylate cyclase activity was also observed at different concentrations of PGE2 and PGA2 (0.25-10 microM). The ATP-dependent uptake of calcium was reduced by approximately 60% in microsomal membranes treated with PGE2 and PGA2. The allosteric properties of Ca2+-stimulated ATPase by Na+, and of guanylate cyclase by Mn.GTP (as reflected by changes in the Hill coefficients, h) were modulated by PGE2 and PGA2. The apparent cooperativity of the Ca2+-ATPase (h + 1.73 +/- 0.21) in control membranes was abolished (h + 1.1 +/- 0.11 and h = 0.9 +/- 0.09) in membranes treated by PGE2 and PGA2 (10 microM), while the allosteric stimulation of guanylate cyclase by Mn.GTP was reduced from h = 2.78 +/- 0.24 in control membranes to h = 1.92 +/- 0.16 and h = 1.73 +/- 0.15 in membranes treated by PGE2 and PGA2 (10 microM), respectively, suggesting that the physical state of Ca2+-stimulated ATPase and guanylate cyclase lipid microenvironments changed from a gel phase to a liquid-crystalline phase. In conclusion, it is suggested that PGE2 and PGA2 promote a phase separation in Walker-256 tumour microsomal membranes. This may be relevant to the Ca2+-calmodulin system and tumour growth inhibition.
在50微摩尔消炎痛存在的情况下，将前列腺素E2（PGE2）和前列腺素A2（PGA2）与从Walker - 256肿瘤中分离出的微粒体膜在25摄氏度下孵育30分钟，使用1,6 - 二苯基 - 1,3,5 - 己三烯（DPH）作为探针，通过稳态荧光各向异性[(r0/r)-1]-1来估计脂质流动性增加情况。Walker - 256肿瘤的微粒体制剂含有钙刺激和镁依赖的ATP酶以及钙调蛋白依赖的鸟苷酸环化酶活性。当制剂用10微摩尔PGE2和PGA2处理时，观察到钙刺激的ATP酶活性显著降低（约65%）。在不同浓度的PGE2和PGA2（0.25 - 10微摩尔）下，还观察到钙调蛋白依赖的鸟苷酸环化酶活性急剧逐渐下降。用PGE2和PGA2处理的微粒体膜中，钙的ATP依赖摄取减少了约60%。PGE2和PGA2调节了Na + 对钙刺激的ATP酶以及Mn.GTP对鸟苷酸环化酶的变构性质（通过希尔系数h的变化反映）。在对照膜中，钙ATP酶的表观协同性（h = 1.73 ± 0.21）在用PGE2和PGA2（10微摩尔）处理的膜中消失（h = 1.1 ± 0.11和h = 0.9 ± 0.09），而Mn.GTP对鸟苷酸环化酶的变构刺激从对照膜中的h = 2.78 ± 0.24分别降低到用PGE2和PGA2（10微摩尔）处理的膜中的h = 1.92 ± 0.16和h = 1.73 ± 0.15，这表明钙刺激的ATP酶和鸟苷酸环化酶脂质微环境的物理状态从凝胶相转变为液晶相。总之，提示PGE2和PGA2促进Walker - 256肿瘤微粒体膜中的相分离。这可能与钙 - 钙调蛋白系统及肿瘤生长抑制有关。
