PLASMA AND LIPOPROTEIN LIPID-COMPOSITION AND HEPATIC ANTIOXIDANT STATUS IN SPONTANEOUSLY HYPERTENSIVE (SHR) AND NORMOTENSIVE (WKY) RATS

Plasma and lipoprotein lipid composition and endogenous hepatic antiox idant status were investigated in hypertensive, 14-week-old spontaneou sly hypertensive (SHR) and normotensive Wistar-Kyoto (WKY) rats fed a standard commercial rat chow. Total plasma calcium and magnesium conce ntrations were similar between both rat strains; however, systolic blo od pressure in SHR was greater than in WKY at 13 weeks of age (197 +/- 12 vs. 132 +/- 14 mmHg; p less than or equal to 0.05), confirming hyp ertension in SHR. Total plasma cholesterol and triacylglycerol concent rations were lower (p less than or equal to 0.05) in SHR compared with WKY. A lower (p < 0.05) HDL cholesterol level in SHR plasma resulted in a higher LDL to HDL cholesterol ratio compared with WKY counterpart s. No significant differences in the relative proportion of HDL apolip oprotein A-I fraction were observed between SHR and WKY. Both SHR VLDL and HDL triacylglycerol fractions were lower (p < 0.05) in SHR than W KY. Analysis of liver antioxidant enzyme activities showed no differen ces in rat Liver superoxide dismutase (SOD), but lower (p < 0.05) live r glutathione peroxidase (GSH-Px) activity in SHR. However, liver glut athione (GSH) levels were similar in SHR and WKY counterparts. A possi ble compensatory effect to the oxidative status of SHR was suggested b y the significant (p < 0.05) increase in both liver catalase (CAT) and glutathione reductase (GSSG-Red) activities. Despite these results, i n vitro oxidative challenge studies with H2O2 demonstrated a greater s usceptibility of liver to GSH depletion in the SHR, although no parall el change in thiobarbituric acid reactive substances (TBARS) productio n was observed. The comparatively lower plasma cholesterol observed in hypertensive SHR paralleled specific differences in Liver catalase an d glutathione redox antioxidant enzyme activities.