磷酸胆碱
洋地黄素
维拉帕米
胞浆
离子载体
化学
钙
微粒体
加压素
生物化学
生物
内分泌学
磷脂酰胆碱
磷脂
体外
酶
膜
有机化学
作者
Jasbinder S. Sanghera,Dennis E. Vance
出处
期刊:Biochimica et biophysica acta
[Elsevier]
日期:1989-06-01
卷期号:1003 (3): 284-292
被引量:13
标识
DOI:10.1016/0005-2760(89)90234-8
摘要
The effects of Ca2+, ionophore A23187, and vasopressin on CTP: phosphocholine cytidylyltransferase were investigated. Cytidylyltransferase is present in the cytosol and in a membrane-bound form on the microsomes. Digitonin treatment caused release of the cytosolic form rapidly. Addition of 7 mM Ca2+ to hepatocyte medium resulted in a 3-fold decrease in cytidylyltransferase released by digitonin treatment (1.7 ± 0.1 nmol/min per mg compared to 5.1 ± 0.2 nmol/min per mg in the control). Verapamil, a calcium channel blocker, partially overcame this effect of Ca2+. Ionophore A23187 and vasopressin both mimicked the effect of Ca2+ and resulted in a decrease in cytidylyltransferase release (2.4 ± 0.1 nmol/min per mg and 2.5 ± 0.2 nmol/min per mg, respectively) compared to control (3.4 ± 0.1 nmol/min per mg). In agreement with the digitonin experiments, incubation with 7 mM Ca2+ resulted in a decrease in cytidylyltransferase in the cytosol (from 4.0 to 1.2 mol/min per mg) and a corresponding increase in the microsomes (from 0.6 to 2.4 nmol/min per mg). Verapamil partially blocked this translocation caused by Ca2+. Ionophore A23187 and vasopressin also caused translocation of the cytidylyltransferase from the cytosol to the microsomes. The addition of Ca2+ also resulted in an increase in PC synthesis. With 7 mM Ca2+ in the medium, the label associated with PC increased to 3.8 ± 0.1·106dpm/dish from 2.7 ± 0.1·106dpm/dish after 10 min. PC degradation was also affected, since 7 mM Ca2+ in the medium resulted in an increase in LPC formation both in the cell and the medium. We conclude that high concentrations of calcium in the hepatocyte medium can cause a stimulation of CTP: phosphocholine cytidylyltransferase and PC synthesis in cultured hepatocytes.
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