Lipid peroxidation, uric acid and xanthine oxidase activity in essential hypertension: mysterious role of uric acid

Abstract

This study was designed to determine, whether there is hyperuricaemia and increased xanthine oxidase activity in essential hypertensive patients in relation to increased free radical generation and to identify uric acid as one of the predictors of hypertension compared to the other blood pressure related factors such as cholesterol, urea and creatinine. Total fifty two mild to moderate hypertensive (male- 29, female- 23, treated45, utreated-7, mean age 50.41±10.73 yr.) and 52 normotensive (male-19, female-33, mean age 44.25±7.44 yr.) samples were studied. All the samples were selected without any family history of gout, hypertension, diabetes as well as any debilitating disease. Five ml or venous blood were collected, and plasma obtained by using EDTA were used for xanthine oxidase activity. Serum uric acid, urea and creatinine were measured by using auto analyser, while plasma xanthine oxidase were via spectrophotometry. Serum lipid peroxide were measured as thiobarbituric acid reaction product by spectrofluorometry. Computer program STATISTICA was used for overall data analysis. Results from our study showed that serum uric acid were consistently higher in hypertensive (H) compared to normotensive (N) [N: 301.33±80.19 mmol/l, H: 396.00±107.71 mmol/ml; p<0.001]. Xanthine oxidase enzyme activity was significantly higher in normotensive than the hypertensive samples (N:2.43±1.12 nmol O2,/ ml plasma/min, H:1.67±1.12nmol O2/ml plasma/ min: p><0.001). Lipid peroxides were significantly higher in hypertensive than the normal (N:3.31±0.33, H:4.49±0.2 nmol MDA equiv/ml; p><0.001). For correlation study we found mean arterial pressure (MAP) significantly correlated with uric acid (r=0.51, p><0.001) and xanthine oxidase activity (r=0.39, p><0.005) in normal sample. Absence of similar correlation in hypertensive samples suggest that uric acid production in hypertensives may serve a different purpose. In conclusion from this study were found that hypertensives with a normal renal function have higher serum uric acid and lipid peroxide but low xanthine oxidase enzyme activity.>