An investigation of the importance of the adrenal gland to the action of dopamine in the rat kidney.

1 In the rat, administration of dopamine is associated with diuresis, natriuresis and a decreased excretion of K+. The site of action of dopamine in mediating these responses has been investigated. 2 Urine volume, and urinary Na+, K+, Cl- and dopamine concentrations have been measured in adrenalectomized and sham-operated male Wist ar rats. 3 As expected, adrenalectomy decreased urine volume and increased Na+ and Cl- excretion; at the same time the amount of dopamine excreted fell, and K+ excretion did not change. 4 Administration of either 3% NaCl (20 ml/kg orally) or frusemide (100 mg/kg s.c.) significantly elevated dopamine excretion after adrenalectomy. 5 When dopamine, 1, 10 and 30 mg/kg (s.c.) was given to adrenalectomized rats, the diuresis and fall in K+ excretion seen in control animals was still present. No further natriuresis, over and above the already high urinary Na+ levels, was observed. 6 The results show that the three actions of dopamine in inducing diuresis and natriuresis, and decreasing K+ excretion, are clearly separable. 7 It is further argued that in mediating these effects the main site of action of dopamine is the kidney rather than the adrenal gland.