Decreased peripheral dopaminergic activity in essential hypertension?

In 42 men aged 50 +/- 1 years with untreated, sustained essential hypertension and in 34 age-matched normotensive men plasma free dopamine concentrations in venous blood in the standing position were more than 60% higher than supine values indicating dopamine involvement in the orthostatic response. In both the hypertensive and normotensive group supine arterial plasma dopamine concentrations were significantly higher than venous supine (P less than 0.004) indicating release of this catecholamine from central organs such as brain, kidneys or adrenals. In the hypertensive group both venous supine, arterial and venous standing plasma dopamine concentrations and the urinary excretion of this catecholamine were lower than in the normotensive group. Between the groups, statistical significance was achieved for venous standing dopamine concentrations (P less than 0.04) and when venous supine, arterial and standing plasma concentrations were added together for each individual (P less than 0.03). The findings may indicate decreased peripheral dopaminergic activity in patients with essential hypertension.