Effects of deep-frying oil on blood pressure and oxidative stress in spontaneously hypertensive and normotensive rats

Objective: Ingestion of deep-frying oil has been reported to cause physiologic and histologic changes in experimental animals' tissue, increase the oxidative stress, and possibly lead to death. The purpose of this study was to investigate the effect of deep-frying oil on oxidative stress and blood pressure in spontaneously hypertensive (SHR) and Wistar Kyoto (WKY) rats. Methods: Deep-frying oil was prepared by frying fresh soybean oil at 180 +/- 5 degrees C for 8 h each day, for 4 consecutive days. Male SHR and WKY rats were fed diets containing 15% fresh soybean oil or deep-frying oil (DO) for 10 wk. Results: Rats ingesting the DO diet had lower feed efficiency and higher relative liver and kidney weights but deep frying had no significant influence on blood pressure in WKY or SHR rats. The DO diet had no effect on plasma renin activity, aldosterone content, or tissue angiotension-I-converting enzyme activity. WKY rats fed the DO diet showed significantly increased urinary thromboxane B-2 and 8-iso-prostaglandin F-2 alpha but not urinary 6-keto-prostaglandin F-1 alpha excretion. Diets containing deep-frying oil resulted in increased plasma thiobarbituric acid-reactive substances and nitric oxide contents and decreased plasma total antioxidant: capacity in SHR and WKY rats. Conclusion: The ingestion of deep-frying oil seemed not to influence blood pressure or its related parameters, but altered eicosanoid metabolism and elevated oxidative stress in SHR and WKY rats. (C) 2010 Published by Elsevier Inc.