Frølich K W, Aarbakke G M, Holmsen H
Department of Biochemistry, University of Bergen, Norway.
Biochem Pharmacol. 1992 Nov 17;44(10):2013-20. doi: 10.1016/0006-2952(92)90104-q.
Non-permeabilizing concentrations (< 40 microM) of chlorpromazine (CPZ) increase the radioactivity of phosphatidylinositol-4-phosphate (PIP) in platelets pre-labelled with [32P]Pi, but the biochemical mechanisms underlying this increase are poorly understood. Incubation of [32P]Pi-labelled, gel-filtered platelets with 25 microM CPZ for 10 min increased: (1) the mass of PIP from 315 to 476 nmol/10(11) platelets but not the total inositol phospholipid mass, (2) the specific phosphodiester radioactivities in phosphatidylinositol (PI), PIP and phosphatidylinositol-4,5-bisphosphate (PIP2) by 34, 63 and 37%, respectively, and (3) the specific phosphomonoester radioactivities in PIP and PIP2 by 53 and 10%, respectively. In control platelets (no CPZ) the specific radioactivity of the phosphodiester was the same in PI, PIP and PIP2, and the specific radioactivity in the phosphomonoester in PIP and PIP2 was 55% of that of the gamma-phosphoryl in ATP, measured as metabolically active, actin-bound ADP. These results suggest that 55% of each of PI, PIP and PIP2 constitutes a metabolic pool which is labelled by 32P in the platelets, while the remainder is in a metabolically inactive pool and not labelled. CPZ has two major effects: (1) CPZ interferes with the kinase and phosphohydrolase reactions that maintain the steady-state level of PIP in the metabolic phosphoinositide pool, resulting in a 92% increase in the PIP level of this pool, and (2) CPZ causes synthesis (45% in 10 min) of new phosphodiester in the metabolically active phosphoinositides by tentative stimulation of the turnover of the phosphoinositide cycle, de novo phosphoinositide synthesis and/or diacylglycerol formation through phospholipases C and D. The marked alteration by CPZ of phosphoinositide metabolism may be part of the mechanism by which this drug effects its psychotropic action.
非通透浓度（<40微摩尔）的氯丙嗪（CPZ）可增加预先用[32P]Pi标记的血小板中磷脂酰肌醇-4-磷酸（PIP）的放射性，但这种增加背后的生化机制尚不清楚。将[32P]Pi标记的、经凝胶过滤的血小板与25微摩尔CPZ孵育10分钟可使：（1）PIP的量从315纳摩尔/10^11个血小板增加到476纳摩尔/10^11个血小板，但总肌醇磷脂量未增加；（2）磷脂酰肌醇（PI）、PIP和磷脂酰肌醇-4,5-二磷酸（PIP2）中的特定磷酸二酯放射性分别增加34%、63%和37%；（3）PIP和PIP2中的特定磷酸单酯放射性分别增加53%和10%。在对照血小板（无CPZ）中，PI、PIP和PIP2中磷酸二酯的比放射性相同，PIP和PIP2中磷酸单酯的比放射性是作为代谢活性的、肌动蛋白结合的ADP测量的ATP中γ-磷酸的55%。这些结果表明，PI、PIP和PIP2各自的55%构成一个代谢池，在血小板中被32P标记，而其余部分处于代谢非活性池中且未被标记。CPZ有两个主要作用：（1）CPZ干扰维持代谢性磷酸肌醇池中PIP稳态水平的激酶和磷酸水解酶反应，导致该池中PIP水平增加92%；（2）CPZ通过暂时刺激磷酸肌醇循环的周转、从头磷酸肌醇合成和/或通过磷脂酶C和D形成二酰基甘油，导致代谢活性磷酸肌醇中合成新的磷酸二酯（10分钟内增加45%）。CPZ对磷酸肌醇代谢的显著改变可能是该药物发挥其精神作用机制的一部分。
