Vig P J, Desaiah D
Department of Neurology, University of Mississippi Medical Center, Jackson 39216.
Neurotoxicology. 1991 Fall;12(3):595-601.
Protein Kinase C (PKC), a Ca(2+)-dependent and phospholipid activated enzyme, regulates a variety of intracellular and extracellular signals across the neuronal membrane. A number of Ca(2+)-dependent enzymes are PKC substrates. PKC activity is modulated by lipophilic compounds including calmodulin inhibitors. Amiodarone, an antiarrhythmic drug is associated with some neurologic and pulmonary side effects and has been shown to interact with calmodulin. The present study describes the effects of amiodarone and desethylamiodarone, a major metabolite of amiodarone, on PKC activity. PKC was partially purified from rat brain on an anion exchange column (DE-52). The interaction of amiodarone and desethylamiodarone with PKC was studied as a measure of altered protein phosphorylation and 3H-phorbol 12, 13-dibutyrate (PDBu) binding. Desethylamiodarone significantly inhibited phosphatidylserine, diacylglycerol and Ca2+ stimulated PKC activity with IC50 of 30 microM. However, amiodarone had no significant effect on PKC activity. Both amiodarone and desethylamiodarone altered the 3H-PDBu binding to PKC and the effect was biphasic. The Scatchard analysis of 3H-PDBu binding to PKC revealed that at lower concentrations (5 microM), amiodarone and desethylamiodarone increased 3H-PDBu binding to PKC with decreased affinity. Whereas, at higher concentrations (greater than 30 microM) these drugs decreased the 3H-PDBu binding. In the presence of Ca2+, phosphatidylserine and PDBu (120 nM) no significant stimulation was observed with low concentrations of amiodarone and desethylamiodarone. However, at high concentrations (50 microM), desethylamiodarone inhibited the PDBu stimulated PKC activity. These data clearly demonstrate that desethylamiodarone a metabolite of amiodarone is a potent inhibitor of PKC activity.(ABSTRACT TRUNCATED AT 250 WORDS)
蛋白激酶C（PKC）是一种钙依赖且受磷脂激活的酶，可调节跨越神经元膜的多种细胞内和细胞外信号。许多钙依赖酶是PKC的底物。PKC活性受包括钙调蛋白抑制剂在内的亲脂性化合物调节。胺碘酮是一种抗心律失常药物，与一些神经和肺部副作用有关，且已被证明可与钙调蛋白相互作用。本研究描述了胺碘酮及其主要代谢产物去乙基胺碘酮对PKC活性的影响。PKC通过阴离子交换柱（DE-52）从大鼠脑中部分纯化。研究了胺碘酮和去乙基胺碘酮与PKC的相互作用，以此作为蛋白质磷酸化改变和3H-佛波醇12,13-二丁酸酯（PDBu）结合的指标。去乙基胺碘酮显著抑制磷脂酰丝氨酸、二酰基甘油和Ca2+刺激的PKC活性，IC50为30 microM。然而，胺碘酮对PKC活性无显著影响。胺碘酮和去乙基胺碘酮均改变了3H-PDBu与PKC的结合，且这种影响是双相的。对3H-PDBu与PKC结合的Scatchard分析表明，在较低浓度（5 microM）时，胺碘酮和去乙基胺碘酮增加了3H-PDBu与PKC的结合，但亲和力降低。而在较高浓度（大于30 microM）时，这些药物降低了3H-PDBu的结合。在存在Ca2+、磷脂酰丝氨酸和PDBu（120 nM）的情况下，低浓度的胺碘酮和去乙基胺碘酮未观察到显著刺激作用。然而，在高浓度（50 microM）时，去乙基胺碘酮抑制了PDBu刺激的PKC活性。这些数据清楚地表明，胺碘酮的代谢产物去乙基胺碘酮是PKC活性的有效抑制剂。（摘要截短于250字）
