Takahashi M, Miura Y, Sano N, Ohzeki T, Sugawara T, Noshiro T, Meguro Y, Watanabe H, Shimizu K, Hanew K
Second Department of Internal Medicine, Tohoku University School of Medicine, Sendai, Japan.
Nihon Naibunpi Gakkai Zasshi. 1988 Nov 20;64(11):1157-68. doi: 10.1507/endocrine1927.64.11_1157.
To investigate the effects of dietary sodium on the peripheral dopaminergic mechanism, changes of unconjugated plasma dopamine(DA) and its related humoral factors were studied in 8 patients with essential hypertension(EH) and 8 age-matched normal controls(N) while they were receiving ordinary meals (Na, 130-180 mEq daily) followed by higher sodium (250-300 mEq daily) diets for a week. Plasma and urinary DA, norepinephrine(NE) and epinephrine(E) were measured by the highly sensitive COMT-mediated radioenzymatic procedure, which permits an accurate estimation of plasma DA as low as 5-6 pg/ml. Under high sodium diets, blood pressure and heart rate were not changed significantly in N and EH subjects. Urinary NE and E tended to decrease, while urinary DA increased significantly in both groups of subjects (p less than 0.05). There was a significant correlation between urinary sodium and DA (r = 0.590, p less than 0.001), but plasma DA failed to correlate significantly to urinary sodium or DA in all subjects. Plasma NE and E tended to decrease in both N and EH subjects, while plasma DA increased significantly (p less than 0.05) in EH from 7.2 +/- 0.8 pg/ml [mean +/- SEM] to 9.3 +/- 1.0 and slightly in N from 9.1 +/- 1.8 to 11.2 +/- 1.3. Plasma renin activity(PRA) and plasma aldosterone(PAC) were invariably decreased in all subjects, while plasma prolactin(PRL) remained unchanged. A significant correlation was observed between plasma DA and NE under ordinary meals (r = 0.733, p less than 0.01), but this correlation disappeared under high sodium diets. Plasma DA showed an inverse correlation to PAC (r = 0.351, p less than 0.05) under both dietary conditions. Upright posture induced a significant rise (p less than 0.05) in NE, E, DA, PRA and PAC with ordinary meals, but the responses of NE and PAC were apparently attenuated with high sodium diets. An intravenous injection of metoclopramide (MCP, 10 mg), a DA receptor antagonist, provoked a slight rise in plasma NE and DA with ordinary meals, of which responses were further enhanced with high sodium diets. MCP induced a definite rise in PAC and PRL in all subjects under both dietary conditions (p less than 0.01), while plasma E and PRA remained unchanged after MCP challenge. The results lend support to the view that unconjugated plasma DA could be a useful marker of peripheral dopaminergic activity, which might be a physiological regulator responsible for the suppression of aldosterone secretion and sympathetic nerve activity observed during high sodium intake.
为研究膳食钠对外周多巴胺能机制的影响，我们对8例原发性高血压（EH）患者和8例年龄匹配的正常对照者（N）进行了研究，观察他们在进食普通餐（每日钠摄入量130 - 180 mEq）一周后，接着摄入高钠（每日250 - 300 mEq）饮食一周期间，血浆游离多巴胺（DA）及其相关体液因子的变化。血浆和尿中的DA、去甲肾上腺素（NE）和肾上腺素（E）采用高灵敏度的儿茶酚-O-甲基转移酶（COMT）介导的放射酶法进行测定，该方法能够准确测定低至5 - 6 pg/ml的血浆DA。在高钠饮食条件下，N组和EH组受试者的血压和心率均无显著变化。两组受试者尿NE和E均有下降趋势，而尿DA显著增加（p < 0.05）。尿钠与DA之间存在显著相关性（r = 0.590，p < 0.001），但在所有受试者中，血浆DA与尿钠或尿DA均无显著相关性。N组和EH组受试者血浆NE和E均有下降趋势，而EH组血浆DA从7.2±0.8 pg/ml[均值±标准误]显著增加至9.3±1.0，N组血浆DA从9.1±1.8略有增加至11.2±1.3（p < 0.05）。所有受试者血浆肾素活性（PRA）和血浆醛固酮（PAC）均持续下降，而血浆催乳素（PRL）保持不变。在普通餐条件下，血浆DA与NE之间存在显著相关性（r = 0.733，p < 0.01），但在高钠饮食条件下这种相关性消失。在两种饮食条件下，血浆DA与PAC均呈负相关（r = 0.351，p < 0.05）。普通餐时，直立位可使NE、E、DA、PRA和PAC显著升高（p < 0.05），但高钠饮食时NE和PAC的反应明显减弱。静脉注射多巴胺受体拮抗剂甲氧氯普胺（MCP，10 mg），普通餐时可使血浆NE和DA略有升高，高钠饮食时反应进一步增强。在两种饮食条件下，MCP均可使所有受试者的PAC和PRL明显升高（p < 0.01），而MCP激发后血浆E和PRA保持不变。这些结果支持了以下观点：血浆游离DA可能是外周多巴胺能活性的一个有用标志物，它可能是一种生理调节因子，负责抑制高钠摄入时观察到的醛固酮分泌和交感神经活动。
