Vig P J, Yallapragada P R, Kodavanti P R, Desaiah D
Department of Neurology, University of Mississippi Medical Center, Jackson 39216.
Pharmacol Toxicol. 1991 Jan;68(1):26-33. doi: 10.1111/j.1600-0773.1991.tb01203.x.
Long-term amiodarone therapy is invariably associated with some side effects. Although its mechanism of action, as an antiarrhythmic drug is well understood, the side effect profile of amiodarone is not yet established. To determine possible mechanisms, the interaction of amiodarone and its major metabolite desethylamiodarone with calmodulin was investigated, since calmodulin is known to regulate Ca2+ transport, cell proliferation and the enzymes involved in signal transduction and nucleotide metabolism. The interaction between the drugs and calmodulin was studied by monitoring intrinsic tyrosine fluorescence of calmodulin and by using a fluorescent probe, N-phenyl-1-naphthylamine (NPN). 14C-Chlorpromazine displacement studies were conducted to differentiate the specific binding sites. The effect on the biological activity of calmodulin was determined with calmodulin dependent phosphodiesterase and Ca2(+)-ATPase. The dansyl calmodulin was used as fluorescent probe to study the effect of these drugs on complex formation between calmodulin and phosphodiesterase. Both amiodarone and desethylamiodarone decreased tyrosine fluorescence of calmodulin with IC50 of 4.9 and 4.4 microM respectively and these interactions were Ca2(+)-dependent. NPN fluorescence was also affected in a concentration dependent manner. These drugs also displaced bound 14C-chlorpromazine from calmodulin and the effect was biphasic. However, desethylamiodarone was more potent than amiodarone. The binding of 3H-amiodarone to calmodulin was modified by a variety of compounds, one class of compounds decreased and the other increased 3H-amiodarone binding to calmodulin. Only, desethylamiodarone inhibited the phosphodiesterase activation by calmodulin with IC50 of 13.2 microM without changing the basal enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)
长期使用胺碘酮治疗总是会伴有一些副作用。尽管其作为抗心律失常药物的作用机制已为人熟知，但其副作用情况尚未明确。为确定可能的机制，研究了胺碘酮及其主要代谢产物去乙基胺碘酮与钙调蛋白的相互作用，因为已知钙调蛋白可调节钙离子转运、细胞增殖以及参与信号转导和核苷酸代谢的酶。通过监测钙调蛋白的固有酪氨酸荧光以及使用荧光探针N - 苯基 - 1 - 萘胺（NPN）来研究药物与钙调蛋白之间的相互作用。进行了14C - 氯丙嗪置换研究以区分特异性结合位点。用钙调蛋白依赖性磷酸二酯酶和Ca2(+) - ATP酶来确定对钙调蛋白生物活性的影响。丹磺酰钙调蛋白用作荧光探针来研究这些药物对钙调蛋白与磷酸二酯酶之间复合物形成的影响。胺碘酮和去乙基胺碘酮均降低了钙调蛋白的酪氨酸荧光，IC50分别为4.9和4.4微摩尔，且这些相互作用依赖于Ca2(+)。NPN荧光也以浓度依赖性方式受到影响。这些药物还从钙调蛋白上置换了结合的14C - 氯丙嗪，且作用呈双相性。然而，去乙基胺碘酮比胺碘酮更有效。多种化合物可改变3H - 胺碘酮与钙调蛋白的结合，一类化合物降低而另一类化合物增加3H - 胺碘酮与钙调蛋白的结合。只有去乙基胺碘酮抑制钙调蛋白激活磷酸二酯酶，IC50为13.2微摩尔，且不改变基础酶活性。（摘要截选至250字）
