Endocrine and haemodynamic responses to graded dopamine infusion in essential hypertension.

Hormonal, mean arterial blood pressure, forearm blood flow and heart rate responses to graded dopamine infusion (0.5-2.0 micrograms/kg/min) were examined in 10 men with untreated essential hypertension WHO group I (147 +/- 4/100 +/- 1 mmHg, means +/- SE), and in 10 normotensive men (129 +/- 2/85 +/- 1 mmHg), all 40 years old. Another 12 normotensive men (126 +/- 3/80 +/- 2 mmHg) were given only saline infusion. Dopamine increased heart rate significantly in the hypertensive group (8 +/- 2 beats/min, p less than 0.001), but the heart rate remained unchanged in the normotensive group (1 +/- 1 beats/min, NS). Although dopamine infusion tended to decrease mean blood pressure, the changes were not significantly different from those observed in the control group. No change in forearm blood flow was observed in either group. In the groups given dopamine, prolactin levels decreased only slightly compared to the control group given saline, the decrement tending to be more pronounced in the hypertensive group. Plasma vasopressin remained unchanged in both groups during dopamine infusion. These results indicate that hypertensive patients exhibit increased sensitivity to the cardiovascular effects of dopamine.