1. This study investigated the role of dopamine in the control of adrenal steroidogenesis. Adrenaline, noradrenaline and dopamine have been measured in plasma and in the adrenal zona glomerulosa and medulla of rats fed low, normal and high sodium diets and in zona glomerulosa tissue of rats with adrenal regeneration hypertension (ARH).
2. Adrenal concentrations (means ± se) of adrenaline, noradrenaline and dopamine in rats fed a normal diet were 1471 ± 335, 527 ± 75 and 51 ± 12 nmol/g in the medulla, and 66 ± 17, 18 ± 9 and 6 ± 1 nmol/g in the zona glomerulosa. The dopamine content of the zona glomerulosa was greater than could be accounted for by simple contamination from the medullary catecholamines and is commensurate with that of tissue with dopaminergic innervation.
3. Adrenal noradrenaline and adrenaline concentrations and plasma catecholamine and corticosterone concentrations were not affected by dietary sodium intake. Plasma aldosterone concentrations were > 3030.4, 339.8 ± 41.5 and 55.2 ± 11.0 pmol/l in rats fed low, normal and high sodium diets respectively.
4. Five weeks after right adrenalectomy and nephrectomy and left adrenal enucleation, ARH rat systolic blood pressure had increased by 47 mmHg. In the regenerated gland, the concentrations of noradrenaline and adrenaline were negligible but dopamine was present in amounts similar to that of a normal adrenal cortex.
5. Dopamine is present in the adrenal zona glomerulosa in significant amounts but does not decrease when dietary sodium intake is reduced and is not inversely related to aldosterone secretion. These observations are compatible with findings in vivo which indicate that dopamine inhibits aldosterone secretion by an extra-adrenal process involving increased clearance of the major aldosterone trophin angiotensin II.