Liposomal and Non-Liposomal Formulations of Vitamin C: Comparison of the Antihypertensive and Vascular Modifying Activity in Renovascular Hypertensive Rats.

Background: Liposomes constitute a promising drug delivery vehicle, and are believed to improve drugs' effectiveness. This study was aimed to compare antihypertensive and vascular modifying activities of liposomal and non-liposomal forms of ascorbic acid.
Methods: Forty-nine male Sprague-Dawley rats were randomly divided into seven groups (n=7): A sham vehicle-receiving (Sham-veh), hypertensive (HTN), vehicle-receiving hypertensive (HTN-Veh), two liposomal Ascorbic acid-treated hypertensive at 50 or 100 mg/kg/day (LVC-50 and LVC-100), and two non-liposomal Ascorbic acid-treated hypertensive at 50 or 100 mg/kg/day (VC-50 and VC-100). Systolic blood pressure (SBP) and heart rate (HR) were measured weekly; after 4 weeks, dose-responses to phenylephrine (PE) in the absence and presence of nitro-L-arginine methyl ester (L-NAME), acetylcholine (Ach), and sodium nitroprusside (SNP) were obtained on aortic rings. Data were analyzed with one-way ANOVA and Duncan's multiple range test at a P value of <0.05 using Sigmastat statistical software.
Results: Compared to the non-liposomal form, the liposomal one was associated with more prominent effects on the final SBP. Both forms of Ascorbic acid decreased SBP dose-dependently. The basal and stimulated release of Nitric Oxide (NO) was significantly recovered by both forms of Ascorbic acid. The PE maximal responses were not significantly different between the liposomal and non-liposomal groups (P=0.08). Although the Emax of Ach-relaxation response was not different in two preparation forms, Ach-relaxation response induced a lower concentration of the liposomal form of Ascorbic acid (P=0.03.
Conclusion: The liposomal Ascorbic acid exhibited relaxation activity in significantly lower concentrations. The observed effects were partly mediated by the increased basal release of NO.
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