Cohen B E, Benaim G, Ruiz M C, Michelangeli F
Centro de Biología Celular, Facultad de Ciencias, Universidad Central de Venezuela, Caracas.
FEBS Lett. 1990 Jan 1;259(2):286-8. doi: 10.1016/0014-5793(90)80028-h.
The mode of action of the polyene antibiotic amphotericin B (AmB), the drug of choice for the treatment of systemic fungal infections and visceral leishmaniasis, is still unclear. An increase in intracellular Ca2+ concentration [( Ca2+]i), toxic in many cases, has been postulated as a possible lethal mechanism for AmB. Cell permeabilization to ethidium bromide (EB) was used as a criterion of viability. Kinetics of the DNA-EB fluorescent complex formation was studied in ergosterol-containing Leishmania promastigotes. Intracellular Ca2+ concentration was measured using quin-2 fluorescence in parallel aliquots. It is shown in this work that AmB can act as an efficient Ca2+ ionophore. However, the rapid permeabilization effect induced by AmB on these cells was not dependent on an increase in [Ca2+]i. On the contrary, it was found that leishmanicidal effect of AmB was enhanced in the absence of external calcium. Furthermore, A23187 a Ca2+ ionophore did not provoke cell permeabilization to EB.
多烯抗生素两性霉素B（AmB）是治疗系统性真菌感染和内脏利什曼病的首选药物，其作用模式仍不清楚。细胞内Ca2+浓度[Ca2+]i升高在许多情况下具有毒性，已被假定为AmB可能的致死机制。细胞对溴化乙锭（EB）的通透性作为活力的标准。在含麦角固醇的利什曼原鞭毛虫中研究了DNA-EB荧光复合物形成的动力学。使用喹啉-2荧光平行测定细胞内Ca2+浓度。这项研究表明，AmB可以作为一种有效的Ca2+离子载体。然而，AmB对这些细胞诱导的快速通透效应并不依赖于[Ca2+]i的增加。相反，发现在没有外部钙的情况下，AmB的杀利什曼原虫作用增强。此外，Ca2+离子载体A23187不会引起细胞对EB的通透。
