Dopamine-1 and dopamine-2 mechanisms in the control of renal function

Dopamine (DA), a catecholamine produced in the kidney, is a renal vasodilator and natriuretic substance, but its action at dopamine-1 (DA-1), dopamine-2 (DA-2) and alpha- and beta-adrenergic receptors limits its effectiveness as a heuristic tool and pharmacologic agent. We have studied the effects of highly selective DA-1 and DA-2 receptor agonists and antagonists in normal human subjects and experimental animals to determine the precise physiological role of renal dopamine at DA-1 and DA-2 receptors within the kidney. We studied fenoldopam, a selective DA-1 agonist, in normal human subjects in metabolic balances at high (300 mEq/day) and low (10 mEq/day) sodium (Na) intake. Selective DA-1 receptor stimulation during high Na intake resulted in renal vasodilation, natriuresis and diuresis in a sustained manner for 3 hours. The natriuresis was mediated by a reduction in Na reabsorption at both proximal and distal tubular sites. In contrast, during low Na intake, DA-1 receptor stimulation did not engender a natriuretic or diuretic response. Thus, sodium depletion may inhibit the function of renal tubular cells in response to DA-1 stimulation. DA-1 receptors are present in the medial layer of the renal vasculature, proximal tubule and cortical collecting duct; DA-2 receptors are localized to the glomerulus, the renal nerves surrounding renal blood vessels and possibly the renal vascular endothelium. We have performed studies in conscious dogs with indwelling renal arterial catheters to identify the physiological role of renal DA to DA-1 and DA-2 receptors.(ABSTRACT TRUNCATED AT 250 WORDS)