Investigation of urinary dopamine as a marker of renal function and clinical application to laboratory medicine

采用大鼠肾切除、去肾神经支配和多巴脱羧酶抑制剂卡比多巴处理，研究尿中多巴胺的来源。尿中排泄的游离多巴胺来源于肾小管多巴胺，其在近端小管合成并调节尿钠排泄和利尿。尿中排泄的结合多巴胺来源于肾过滤的多巴胺，而肾过滤的多巴胺来源于血浆中的结合多巴胺。由于血浆结合多巴胺在肾小球滤过，肾功能损害患者血浆结合多巴胺升高。利用尿游离多巴胺、尿结合多巴胺和血浆结合多巴胺的这些参数，可以评价肾功能。我们研究了尿多巴胺水平作为肾功能，特别是肾小管活动的标志物的有用性。我们确定了慢性肾小球肾炎患者和健康志愿者尿中游离多巴胺水平与一些已确定的肾功能标志物之间的相关性。尿游离多巴胺水平与血肌酐、尿α 1-微球蛋白、尿β 2-微球蛋白呈负相关，与尿肌酐、尿素氮、尿钾、尿无机磷呈正相关。研究结果表明，尿多巴胺水平是肾功能的指标，尿游离多巴胺水平的测量是有用的评估肾功能损害。

The origin of dopamine in urine was investigated using rats nephrectomized, denervated the renal nerve and treated with carbidopa, an inhibitor of DOPA decarboxylase. The free dopamine excreted in urine is derived from renal tubular dopamine, which is synthesized at proximal tubules and regulates both natriuresis and diuresis. The conjugated dopamine excreted in urine is derived from renal filtrated dopamine, which is originated from the conjugated dopamine in plasma. As the plasma conjugated dopamine is filtrated at glomerulus, the plasma conjugated dopamine elevates in the patients with impaired renal function. Using these parameters of urinary free dopamine, urinary conjugated dopamine and plasma conjugated dopamine, it is possible to evaluate the renal function. We investigated the usefulness of the urinary level of dopamine as a marker of renal function, especially of tubular activity. We determined the correlations between the urinary level of free dopamine and a number of established markers of renal function in patients with chronic glomerulonephritis and healthy volunteers. The urinary level of free dopamine was negatively correlated with the serum level of creatinine and the urinary levels of alpha1-and beta2-microglobulins, and was positively correlated with urinary level of creatinine, urea nitrogen, potassium and inorganic phosphorus. Findings suggest that the urinary level of dopamine is an index of renal functions and that measurements of the urinary level of free dopamine are useful for evaluating renal impairment.