Hokin-Neaverson M, Sadeghian K
J Biol Chem. 1984 Apr 10;259(7):4346-52.
Dispersed mouse pancreas acinar cells were prepared in which phosphatidylinositol had been labeled with myo[2-3H]inositol. During incubation with 0.3 microM cholecystokinin octapeptide (CCK-8) for 15 min, there was a loss of [3H]phosphatidylinositol radioactivity (23%) and a 3-fold gain in trichloroacetic acid-soluble radioactivity. Replacement of NaCl by up to 58 mM LiCl did not significantly affect the amount of CCK-8-stimulated [3H]phosphatidylinositol breakdown or the gain in acid-soluble radioactivity. However, in normal medium, the product of phosphatidylinositol breakdown was almost all inositol, whereas in Li+-containing medium, the product was almost all inositol 1-phosphate. Similar results were obtained with acetylcholine which, in the presence of Li+, gave a dose-responsive increase in inositol 1-phosphate over the concentration range of 0.1 to 10 microM. No increased accumulation of [3H]inositol diphosphate or [3H]inositol triphosphate was detected in stimulated cells. Time courses in the presence of Li+ indicated that the formation of inositol 1-phosphate preceded the formation of inositol. Addition of up to 50 mM myoinositol to the incubation medium showed no diluting effect on the amount of [3H]inositol 1-phosphate found. The accumulation of inositol 1-phosphate is presumably due to the known ability of Li+ to inhibit myoinositol 1-phosphatase. The results provide clear evidence that stimulated phosphatidylinositol breakdown involves a phospholipase C type of phosphodiesterase activity. 1.25 mM Li+ gave half-maximal inositol 1-phosphate accumulation. This is close to the range of plasma Li+ levels which is used therapeutically in psychiatric disorders. In unstimulated cells, [3H]inositol 1-phosphate accumulation in the presence of Li+ corresponded to a breakdown rate for [3H]phosphatidylinositol of 2 to 3%/h.
制备了用肌醇[2-³H]肌醇标记磷脂酰肌醇的分散小鼠胰腺腺泡细胞。在用0.3微摩尔胆囊收缩素八肽（CCK-8）孵育15分钟期间，[³H]磷脂酰肌醇放射性损失（23%），三氯乙酸可溶性放射性增加了3倍。用高达58毫摩尔氯化锂替代氯化钠对CCK-8刺激的[³H]磷脂酰肌醇分解量或酸溶性放射性增加没有显著影响。然而，在正常培养基中，磷脂酰肌醇分解产物几乎全是肌醇，而在含锂培养基中，产物几乎全是肌醇1-磷酸。乙酰胆碱也得到了类似结果，在锂存在的情况下，在0.1至10微摩尔的浓度范围内，肌醇1-磷酸呈剂量反应性增加。在受刺激的细胞中未检测到[³H]肌醇二磷酸或[³H]肌醇三磷酸的积累增加。在锂存在下的时间进程表明，肌醇1-磷酸的形成先于肌醇的形成。向孵育培养基中添加高达50毫摩尔的肌醇对所发现的[³H]肌醇1-磷酸量没有稀释作用。肌醇1-磷酸的积累可能是由于锂已知具有抑制肌醇1-磷酸酶的能力。结果提供了明确证据，表明刺激的磷脂酰肌醇分解涉及磷脂酶C类型的磷酸二酯酶活性。1.25毫摩尔锂使肌醇1-磷酸积累达到最大积累量的一半。这接近用于精神疾病治疗的血浆锂水平范围。在未受刺激的细胞中，锂存在下[³H]肌醇1-磷酸的积累对应于[³H]磷脂酰肌醇2%至3%/小时的分解速率。
