1. Five normal subjects were studied under metabolic conditions on a controlled sodium and potassium intake.

2. Plasma and urine free dopamine concentrations were measured in these subjects before, during and after 5 days administration of fludrocortisone (0·2 mg twice daily).

3. Urine free dopamine showed a tendency to fall during the early phase of fludrocortisone administration and then rose towards normal.

4. In a patient with primary hyperaldosteronism there was no evidence of increased renal production of dopamine. Urine dopamine fell when plasma renin activity rose as a result of spironolactone administration (200 mg three times a day for 5 days).

5. If renal dopamine has a role in mineralocorticoid ‘escape’ then it may be permissive only. The mechanisms of control of dopamine production could include tubular sodium concentration, tubular chloride concentration and intrarenal renin activity.

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