Abnormal adrenal catecholamine synthesis in salt-sensitive Dahl rats.

Abstract

The possible role of catecholamines in the abnormal renal response to salt loading, a genetic defect resulting in hypertension in the salt-sensitive strain of Dahl rats, was investigated by measuring the adrenal synthesis of norepinephrine, epinephrine, and dopamine as well as their content in several tissues and the urinary excretion of these catecholamines as well as some of their metabolites at the height of salt-induced hypertension. We found that salt-sensitive Dahl rats, compared with salt-resistant Dahl rats, have a higher adrenal synthesis of [3H]norepinephrine following a pulse injection of [3H]tyrosine, a higher adrenal norepinephrine and epinephrine content but a lower kidney and heart ventricle content of dopamine and norepinephrine, and a decreased excretion of urinary dopamine, dihydroxyphenylacetic acid, 3-methoxytyramine, and homovanillic acid. These data suggest that the primary abnormality in salt-sensitive Dahl rats may be their inability to turn off, during high salt intake, their increased adrenal norepinephrine synthesis from dopamine. The abnormal catecholamine response of salt-sensitive Dahl rats to high salt intake indirectly suggests increased noradrenergic activity and decreased dopaminergic activity in the kidney, which may be important mechanisms in the sodium retention and hypertension of these rats.