各種高血圧症における血漿遊離型ドーパミン濃度について

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The concentrations of unconjugated plasma dopamine (PDA) were studied in patients with various types of hypertension. Catecholamines were extracted from plasma specimens (1.0-3.0ml) through an Amberlite CG50 (Li+-form) microcolumn and eluted by a magnesium sulfate-ethanol solution. The elute was then desalinated and deproteinized by the ethanol-treated precipition procedure and dried in a vacuum oven at 25°C. A fraction of catecholamines was assayed with the modified procedures of the COMT-mediated radio-enzymatic method. This assay system was sensitive enough to permit an accurate measurement of PDA as low as 6.0pg per ml of plasma without any detectable contamination of the conjugated dopamine. The resting levels of PDA were 10.1 ± 1.0pg/ml (mean ± SEM), 9.5 ± 1.0 and 13.7 ± 0.6 in patients with borderline hypertension (BH, n=25), essential hypertension (EH, n=22) and renovascular hypertension (RVH, n=8), respectively. The values in EH patients were significantly smaller than those in age-matched normal controls (13.0 ± 1.4, n=14, p<0.05). Remarkably increased PDA values were observed in patients with pheochromocytoma (76.5 ± 25.4, n=9, p<0.01). Significantly raised PDA values were also found in patients with primary aldosteronism (PA, 27.8 ± 9.0, n=6, p<0.05), while their plasma norepinephrine levels (PNE, 169 ± 39pg/ml) tended to be lower than those of normal controls (206 ± 20), showing an apparent dissociation between the values of PDA and PNE. Upright posture for 15 minutes induced a significant rise in PDA (p<0.05) in all subjects except PA patients. The postural changes of PDA, however, were invariably smaller than those of PNE (p<0.05). The resting values of PDA in normal, BH and EH patients showed a significant negative correlation with their mean arterial pressures (r=-0.301, n=61, p<0.05) and a positive correlation with those of PNE (r= 0.381, p<0.01). There was no correlation between PDA and age in any group studied. These findings indicate that PDA might not be only a precursor fraction of neurotransmitters released from the sympathetic nervous system but could also represent a physiological function of the dopaminergic regulatory system. The varied but distinctive features of PDA status in various types of hypertension suggest the possibility that the peripheral dopaminergic mechanisms play an inherent role in the pathogenesis of hypertension.

各種高血圧症における血漿遊離型ドーパミン濃度について

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