Nitric oxide activity in childhood hypertension

Abstract

Objectives - To investigate nitric oxide (NO) activity in childhood hypertension using nitrite and nitrate (NOx) concentrations in plasma as an index of nitric oxide generation. Design - Cross sectional study. Settings - Tertiary care paediatric Center and district general hospitals in the UK. Patients - Children attending the above centre for treatment of hypertension. The control subjects were normotensive healthy children attending district general hospitals for minor medical and surgical disorders. Interventions - None. Main outcome measures - Plasma (P) and urinary (U) NOx concentrations, blood pressure, and glomerular filtration rate. Results - Sixteen normal children (mean age 6.9 years), 13 children with renovascular hypertension (mean age 7.8 years), and 25 children with hypertension associated with renal parenchymal disease (mean age 10.7 years) were studied. Mean (SD) P(NOx) values of children with hypertension with renovascular disease (15.3 (11.4) μmol/l) and renal parenchymal disease (18.3 (11.4) μmol/l) were significantly above that of normal children (11.9 (5.9) μmol/l) after accounting for age and glomerular filtration rate influences. Higher concentrations of P(NOx) in normal children were associated with younger age, but not in the children with hypertension. Higher P(NOx) concentrations were also associated with a lower glomerular filtration rate in normal children and children with hypertension with renal parenchymal disease, but not in the children with hypertension with renovascular disease. U(NOx) excretion expressed as a ratio against urine creatinine (U(creat)) excretion was not statistically different among the study groups. Conclusions - P(Nox) is increased in children with hypertension even after statistical elimination of the glomerular filtration rate and age influences. This suggests a normal or increased NO synthase activity in childhood hypertension in contrast with adults with hypertension in whom it is described as reduced.