Abstract
Objective: Mibefradil is a novel calcium channel antagonist that selectively blocks T-channels. It acts to reduce hypertension, is cardioprotective and reduces ischemic episodes. Oxidative modification of low-density lipoproteins (LDL) is well known to contribute to coronary atherosclerosis and we therefore investigated to see whether mibefradil had antioxidative action on LDL.
Methods: Human LDL were isolated by ultracentrifugation. In vitro oxidation of LDL (0.1 μmol · l−1 protein) in the presence of various concentrations of mibefradil was initiated by 3.2 μmol · l−1 copper ions. The kinetics of formation of conjugated dienes was followed photometrically. Malondialdehyde and lipoperoxides were determined at maximum oxidation. LDL (0.3 μmol · l−1) were also pre-incubated with mibefradil (120 μmol · l−1). Excessive mibefradil was separated by column technique. The resultant LDL were oxidized using copper ions or (AAPH) 2,2′-azobis(2-amidinopropane) hydrochloride.
Results: The presence of mibefradil in the concentration range from 10 to 200 μmol · l−1 had dose-dependent effects. These were protection of LDL against oxidation measured as prolongation of the lagtime up to 250%, and reduction in the formation of malondialdehyde down to 65% and of lipoperoxides to 20%. Pre-incubation of LDL with mibefradil prolonged the lagtime of Cu-mediated oxidation up to 132% and of AAPH-mediated oxidation up to 138%.
Conclusion: In addition to the T-channel blocking and antiproliferative effects, our results provide arguments for a protective role of mibefradil (10–200 μmol · l−1) on LDL against in vitro oxidation. This was shown with three independent parameters (lagtime, malondialdehyde and lipoperoxides) and in different oxidation models.
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Received: 11 March 1998 / Accepted in revised form: 1 July 1998
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Leonhardt, W., Lange, M. Antioxidative action of the novel calcium channel antagonist mibefradil on low-density lipoproteins. E J Clin Pharmacol 54, 603–607 (1998). https://doi.org/10.1007/s002280050521
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DOI: https://doi.org/10.1007/s002280050521