Effects of dietary sodium on dopamine content of rat adrenal cortex

Dopamine occurs in the adrenal cortex and appears to provide maximum tonic inhibition of aldosterone secretion. In the present experiments, the effects of high or low sodium (Na+) intake on concentrations of dopamine in the adrenal cortex of adult male Sprague-Dawley rats were examined. In the first experiment, sham-operated and adrenal demedullated rats were provided with 1.5% NaCl or tap water for drinking for 5 days. In the second experiment, sham-operated and adrenal demedullated rats were fed regular laboratory chow (approximately 0.45% NaCl) or low Na+ chow (0.001-0.005% NaCl) for 5 days. High Na+ intake was attended by dramatic increases in fluid consumption, urine production and Na+ excretion. However, high Na+ intake did not affect levels of dopamine, norepinephrine or epinephrine in the adrenal glands. Approximately 45% of adrenal dopamine but less than 4% of either norepinephrine or epinephrine was localized in the adrenal cortex. In the second experiment, animals fed a diet low in Na+ had a significant reduction in Na+ excretion but levels of adrenal catecholamines were unaffected. Approximately 36% of adrenal dopamine but less than 5% of either norepinephrine or epinephrine was localized in the adrenal cortex. These findings suggest that adrenal cortical dopamine concentrations remain relatively constant in spite of presumed differences in turnover rates of this neurohormone.