Changes in Renal Function and Oxidative Status Associated with the Hypotensive Effects of Oleanolic Acid and Related Synthetic Derivatives in Experimental Animals

Abstract

PurposeThe triterpene oleanolic acid (OA) is known to possess antihypertensive actions. In the present study we to compared the effects of the triterpene on mean arterial blood pressure (MAP) and kidney function following acute administration in normotensive animals with those of its related oleanane synthetic derivatives (brominated oleanolic acid, Br-OA and oleanolic acid methyl ester, Me-OA). We also used experimental models of hypertension to further explore the effects of sub-chronic oral OA treatment and evaluated influences on oxidative status.MethodsOA was extracted from dried flower buds of Syzygium aromaticum using a previously validated protocol in our laboratory. Me-OA and Br-OA were synthesized according to a method described. Rats were supplemented with lithium chloride (12 mmol L-1) prior to experimentation in order to raise plasma lithium to allow measurements of lithium clearance and fractional excretion (FELi) as indices of proximal tubular Na+ handling. Anaesthetized animals were continuously infused via the right jugular with 0.077M NaCl. MAP was measured via a cannula inserted in the carotid artery, and urine was collected through a cannula inserted in the bladder. After a 3.5 h equilibration, MAP, urine flow, electrolyte excretion rates were determined for 4 h of 1 h control, 1.5 h treatment and 1.5 h recovery periods. OA, Me-OA and Br-OA were added to the infusate during the treatment period. We evaluated sub-chronic effects on MAP and kidney function in normotensive Wistar rats and in two animal models of hypertension, spontaneously hypertensive rats (SHR) and Dahl salt-sensitive (DSS) rats, during 9-week administration of OA (p.o.). Tissue oxidative status was examined in these animals at the end of the study. Increasing evidence suggests that and renal function disturbances and oxidative stress play major roles in the pathogenesis of hypertension.ResultsAcute infusion OA and oleanane derivatives displayed qualitatively similar effects in decreasing MAP and increasing urinary Na+ outputs. The drugs increased the FENa and FELi without influencing GFR indicating that at least part of the overall natriuretic effect involved proximal tubular Na+ reabsorption. Sub-chronic OA administration (p.o.) also elicited hypotensive responses in Wistar, DSS and SHR rats. The MAP lowering effect was more marked in hypertensive animals and were positively correlated with increased urinary Na+ excretion. Compared with respective control rats, OA treatment reduced malondialdehyde (MDA, a marker of lipid peroxidation) and increased activities of antioxidant enzymes; superoxide dismutase and glutathione peroxidase in hepatic, cardiac and renal tissues.ConclusionsOA and oleanane derivatives have similar effects on MAP, kidney function and oxidative stress. The amelioration of oxidative stress and blood pressure lowering effects by OA are more marked in hypertensive animals and correlated with an increased urinary Na+ output.Novelty of the WorkThe results of this study are novel in that they show 1) a correlatio...

Viscum articulatumBurm. f.: a review on its phytochemistry, pharmacology and traditional uses

“…And also OA reduced the malondialdehyde (MDA) as compared to the control group. [79] Antiepileptic activity Ethnobotanically, the plant is mentioned to be used for epilepsy in Nepal and Darjeeling region of India. Geetha et al (2010) reported the antiepileptic activity of methanolic extract of V. articulatum aerial part in albino rats and mice.…”

The Ameliorative Effect of Pectin-Insulin Patch On Renal Injury in Streptozotocin-Induced Diabetic Rats

“…Systolic (SBP) and diastolic (DBP) blood pressure, body weight, 24-hour water and food consumption and urine output volume were recorded. SBP and DSP were monitored using the non-invasive tail cuff method with photoelectric sensors (IITC Model 31 Computerised Blood Pressure Monitor, Life Sciences, Woodland Hills, California, USA) as previously described [16]. Urine samples were collected for the analysis of nephrin, albumin and creatinine concentration.…”

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“…Mean arterial pressure was monitored using the non-invasive tail-cuff technique with photoelectric sensors (IITC Model 31 Computerised Blood Pressure Monitor; Life Sciences, Woodland Hills, CA, USA), as described previously. 24 All measurements were conducted at 1000 h.…”