A paradoxical fall in urine dopamine output when patients with essential hypertension are given added dietary salt.

The effect of dietary sodium on the urine dopamine excretion of eight hypertensive patients and six matched controls was studied under metabolic balance conditions over a 2 week period during which dietary sodium intake was increased from 20 to 220 mmol/day. The control group showed the expected increase in dopamine excretion in response to sodium but the hypertensive patients showed an initial fall followed by a return to baseline values. Neither group showed a rise in blood pressure but the hypertensive patients showed a greater weight gain on salt loading, although this change was not significant. The cumulative sodium balance was greater and more prolonged in the hypertensive patients, although this difference also did not attain statistical significance. This defect in dopamine mobilization may be important in relation to renal sodium handling by patients with essential hypertension.