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Effects of dietary mg status and susceptibility to hypertension on in-vitro lipid peroxidation in rats Lai, Lucinda Man Lai


This study was designed to determine the association between dietary Mg (Mg) status on induction of hypertension in both normotensive Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR). The particular interest was the link between lipoprotein lipid composition and susceptibility to oxidation and development of hypertension caused by Mg status. Six-week old male SHR and WKY were fed a synthetic diet with varying Mg levels (Mgreplete and deplete) for eight weeks. Two experiments were conducted with animals fed either casein (Experiment I) or soy (Experiment II) protein diets. SHR exhibited significantly (P<0.05) lower plasma cholesterol, triglyceride and phospholipid concentrations than WKY rats, regardless of dietary protein source. In Experiment I, Mg deficiency in casein fed rats significantly (P<0.05) increased plasma and lipoproteins (VLDL and LDL) cholesterol concentrations in both WKY and SHR strains. These results indicated that Mg deficiency significantly (P<0.05) increased plasma and lipoprotein cholesterol concentrations in a similar way in both WKY and SHR rats, regardless of differences in lipid metabolism between these two inbred strains of rats. In Experiment II, the hypercholesterolemic effect of Mg deficiency was diminished when rats were fed a soy-protein diet. Mg deficiency significantly increased plasma cholesterol concentrations only in SHR rats, but not in WKY rats. Lipoproteins isolated from SHR produced less TBARs and fluorescence after 180-min Cu -induced forced peroxidation, and, thereby, were less susceptible to lipid peroxidation, than those isolated from WKY. SHR exhibited significantly (P<0.05) higher systolic blood pressure than WKY rats, and rats fed the Mg-deficient diet showed significantly (P<0.05) higher systolic blood pressure than counterparts fed the Mg-replete diet in both Experiments I and II. Mg deficiency also significantly (P<0.05) enhanced the genetic predisposition of the SHR to hypertension, regardless of dietary protein source. It can be concluded from the present study that greater systolic blood pressure observed in Mg-deficient rats was in agreement with an increased lipoprotein susceptibility to forced peroxidation.

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