Effect of Combined Oral Contraceptive Steroids on Plasma Lipid Peroxidation and Nitric Oxide Biosynthesis in Female Rats

Oral contraceptive (OC) usage is associated with increased cardiovascular risk. The present study investigated the effect of combined OC on plasma lipids, lipid peroxidation, and biosynthesis of nitric oxide (NO). Female Sprague-Dawley rats were treated with OC steroids (10mg/kg ethinyloestradiol + 100mg/kg norgestrel) or drug vehicle for seventy days by gavage. Plasma malondialdehyde (MDA) and urinary NO2/NO3 concentrations were assessed as indicators of lipid peroxidation and biosynthesis of NO respectively. LDL-cholesterol/HDL-cholesterol ratio were taken as atherogenic markers. Results showed that LDL-cholesterol LDL-cholesterol/HDL-cholesterol ratio were significantly higher in OC-treated rat while OC treatment caused significant decreases in plasma HDL-cholesterol and urinary NO2/NO3 levels. However, no significant differences were observed in plasma MDA, total cholesterol and triglyceride levels between both groups of rats. The results of this study suggest that chronic administration of high-dose OC may increase incidence of atherosclerotic cardiovascular disease and further provide evidence that OC use is associated with decreased NO biosynthesis, hypercholesterolaemia and unaltered lipid peroxidation. Keywords: oral contraceptive, cholesterol, lipid peroxidation, nitric oxide.NQJHM Vol. 15 (3) 2005: pp. 143-14