[Application of urinary free dopamine as a marker of renal function, and comparison with other renal marker]

Urinary free dopamine (U-f-DA) is derived from renal DA synthesized in the renal proximal tubules, and plays an important role for diuresis and natriuresis. We were previously reported that U-f-DA was the superior marker of renal function as compared with ordinary methods including alpha 1-microglobulin (U-alpha 1 MG), beta 2-microglobulin (U-beta 2 MG) and N-acetyl-beta-D-glucosaminidase (U-NAG) in spot urine samples. U-f-DA can be used as index for the evaluation of renal transplantation. In order to evaluate the clinical usefulness of U-f-DA as a marker of renal function, we investigated as follows; firstly, the age related changes of U-f-DA in healthy out-patients, secondly, the correlation between U-f-DA and creatinine clearance (CCr), serum creatinine (S-Cr) in in-patients, and thirdly, the chronological changes of U-f-DA, U-alpha 1 MG, U-beta 2 MG, CCr and S-Cr in patients with chronic renal failure before and after renal transplantation. There is no age-related changes in U-f-DA from patients with 3 years to 88 years old. U-f-DA was positively correlated with CCr and negatively correlated with S-Cr. There are parallel changes of U-f-DA and CCr in increasing direction, on the other hand, parallel changes of U-alpha 1 MG, U-beta 2 MG and S-Cr in decreasing direction after renal transplantation. In patients with post renal transplantation who were not well controlled, S-Cr increased gradually with the decreasing level of U-f-DA. These results suggest that the measurement of U-f-DA in spot urine samples is useful marker for evaluation of the renal function and can be used an index of viability of the transplanted kidney.