Peripheral dopamine in hypertension and associated conditions.

The purpose of this study is to review the role of dopamine in hypertension and associated conditions. The analysis of literature indicates that present knowledge is mostly based on poor markers and indirect evidence of dopaminergic activity and only few molecular biological data. Alternative markers such as plasma dopamine sulfate emerge as a possible substitute for the low plasma free dopamine detectability, one of the main obstacles in understanding the relationship between circulating dopamine and its receptor actions in hypertension. Essential hypertension represents a heterogeneous entity: based on evidence in borderline and non-modulating hypertension, the tubular dopamine receptor defect may be compensated by increased dopamine synthesis (dopamine beta-hydroxylase suppression-mediated?) and release; alternatively, compatible with data in stable, salt-sensitive and low renin-hypertension, the receptor defect may be amplified by a deficient dopamine synthesis, basal and in response to salt and volume expansion. Secondary forms of hypertension (renovascular, renal, polycystic kidneys, mineralocorticoid, pheochromocytoma) associated conditions (renal and heart failure, diabetes, hypovolaemia, mastocytosis) or iatrogenic (cocaine abuse) are mostly reflected by increased dopamine indices, some of them proposed to be counteracting the activation of prohypertensive mechanisms. In conclusion dopamine should thus be monitored in hypertension while respecting several associated conditions affecting peripheral dopaminergic activity. Catecholamine synthesis and metabolism enzymes' and dopamine receptors' targeting are essential for advancing the understanding of dopamine's diagnostic and therapeutic implications.