Relationships between Plasma Catecholamines, Renin, Age and Blood Pressure in Essential Hypertension

Abstract

The aim of this study was to examine the interrelationships between age, plasma catecholamines, plasma renin activity (PRA) and blood pressure in essential hypertensive (EH) patients. PRA, plasma noradrenaline (NA) and adrenaline (A) were measured in 76 consecutive EH patients (WHO stages 1–2, aged 24–66 years) and in 28 normotensive subjects (aged 25–64 years) studied at rest in supine position after 5 days of normal fixed sodium and potassium intake. Both plasma NA and A were slightly but significantly higher in EH patients (p < 0.05). While no relationship was found between the various parameters in normotensive subjects, in EH patients, particularly those at WHO stage 2, plasma NA was directly related to mean blood pressure (MBP) (p < 0.001) and PRA (p < 0.01). Plasma A was weakly related to MBP (p < 0.05); PRA was inversely related to age (p < 0.01) but no relationship was found between NA or A and age. Partial correlation analysis confirmed all these relationships. In fact, NA was related to MBP also considering constant PRA (p < 0.001) or age (p < 0.001), and NA was related to PRA also considering constant MBP (p < 0.01) or age (p < 0.001). Acute pharmacological alpha- and beta-blockade, with labetalol 100 mg i.v., induced a reduction of MBP which was directly related to basal plasma NA (p < 0.001). These results support the view that in EH the sympathetic nervous system might be in part responsible for PRA levels and for the severity of hypertension.