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RESEARCH PRODUCT

Protein oxidation in mild essential hypertension

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An intensified oxidative stress has been associated with aging and many disease, including essential hypertension (EH) [6, 11, 16]. In EH an increased level of reactive oxygen and nitrogen species (RONS) may impair the bioavailability of nitric oxide (NO), by inducing its accelerated transformation in peroxynitrite [4]. Beside this, many other pathophysiological processes in EH may be influenced by RONS, considering their harmful effects on the structural and functional properties of lipids, proteins and nucleic acids. Some points need to be further investigated, such as the relationship between oxidative stress and the degree of hypertension, and identification of the most useful marker of enhanced oxidative stress in this clinical condition. In EH several papers showed an increase in lipid peroxidation [1, 7, 13]; this datum was also present in juvenile essential hypertension [17] and in newly diagnosed hypertensives [12]. In other reports, however, normal levels of lipid peroxidation were observed [5, 8]. Fewer papers [3, 7, 10, 14] have examined protein oxidation in EH up to now. Among the indicators of protein oxidation, the most widely used is the concentration of protein carbonyl groups (C= O). These groups are generated by oxidation of protein side chains, and some aminoacidic residues, such as lysine, proline, arginine and threonine are the most involved [15]. In this study we examined protein oxidation expressed as plasma protein carbonyl groups in untreated subjects with mild essential hypertension. We enrolled 23 subjects (17 men and 6 women; mean age 45.05± 6.14 years; range 31–53 years). The diagnosis of hypertension was based on blood pressure (BP) measurements taken on two separate occasions with the patient in a seated position after 15 minutes of rest. The mean values of these measurements were 144/87 mmHg. Only a minority of the patients showed a simultaneous increase of systolic and diastolic BP above 140/90 mmHg, the great majority having only either systolic or diastolic values within the range of hypertension. In all patients an ambulatory BP monitoring was performed: day-time systolic BP and diastolic BP were respectively 134.2± 8.4 and 86.7± 6.1 mmHg, night-time SBP and DBP were respectively 120.5± 11.1 and 75.7± 7.5 mmHg and 24-h SBP and DBP were respectively 128.9± 8.7 and 82.4± 5.7 mmHg. In this group the hypertension duration was 13.4± 11.9 months. The