PLASMA HYDROGEN-PEROXIDE PRODUCTION IN HYPERTENSIVES AND NORMOTENSIVESUBJECTS AT GENETIC RISK OF HYPERTENSION

Background Oxygen free radicals may play roles in hypertension both in arteriolar constriction and in formation of lesions. Objective To qua ntify free radical production in blood plasma of genetic hypertensives . Design Hydrogen peroxide levels were measured, because it is one of the most stable reactive oxygen species. Methods An electrode techniqu e was used to determine plasma hydrogen peroxide levels after blockade of endogenous catalase with sodium azide. This method was validated b y an independent spectrophotometric technique. Results Members of the essential hypertensive group (n = 21) had higher plasma hydrogen perox ide levels (3.16 +/- 0.14 versus 2.50 +/- 0.16 mu mol/l, P = 0.005) th an did members of the normotensive group (n = 29). Furthermore, within the normotensive group, those with a family history of hypertension ( n = 15) exhibited higher hydrogen peroxide levels (2.83 +/- 0.27 versu s 2.14 +/- 0.13 mu mol/l, P = 0.03) than did those without such a fami ly history (n = 14). Plasma hydrogen peroxide levels in these 50 subje cts were correlated to their mean arterial pressures (r = 0.54, P < 0. 001). When hypertensives were grouped with normotensives without a fam ily history of hypertension, the correlation improved (r = 0.70, P < 0 .001). Statistical analysis (two-way analysis of variance) revealed th at a family history of hypertension was a better predictor of plasma h ydrogen peroxide production than was blood pressure status (P = 0.003 versus P = 0.093). Further investigations showed that superoxide is pr oduced in plasma and that one of its sources is xanthine oxidase. Conc lusions Hydrogen peroxide is produced in blood plasma and elevation of its level could constitute a pathogenic factor in vascular organ dama ge attendant upon systemic hypertension. (C) 1998 Rapid Science Ltd.