Circulating dopamine in Raynaud's phenomenon.

Plasma free and conjugated and intraplatelet free dopamine, norepinephrine, and epinephrine levels were determined by high-performance liquid chromatography coupled with electrochemical detection for 20 subjects with Raynaud's phenomenon of various etiologies. Circulating free dopamine and epinephrine were significantly lower in Raynaud's patients than in controls (dopamine 26.0 +/- 13.6 vs 56.3 +/- 39.6 pg/ml, p less than 0.005; epinephrine 25.8 +/- 16.9 vs 56.9 +/- 40.9 pg/ml, p less than 0.005), while the corresponding conjugated forms in plasma and the intraplatelet contents were within normal limits. There were no abnormalities in plasma free, conjugated, or intraplatelet free norepinephrine. All of the levels were independent of the etiology, the duration, and the severity of the disease. The reduced plasma levels of free dopamine and epinephrine might be due to impaired adrenal release in response to some kinds of sympathetic stimulation or to rapid tissue uptake and peripheral metabolism. A possible role for a postischemic dopaminergic vasodilating system is discussed.