Demonstration of N-acetyldopamine in human kidney and urine

Free and conjugated dopamine and N-acetyldopamine concentrations were measured in human urine and kidneys by reversed phase high performance liquid chromatography with single-electrode electrochemical detection. Conjugated N-acetyldopamine was found to occur in urine from six normal humans and in four out of six human kidneys. Unconjugated N-acetyldopamine was detected in only one urine sample and in three of seven kidneys. Urinary excretion of total N-acetyldopamine averaged 0.485 micromoles/day. This compares to a total dopamine excretion of 4.69 micromoles/day in the same subjects. In the kidneys, total N-acetyldopamine concentration averaged 1.46 nanomoles/gram. Total dopamine in the same tissues averaged 5.48 nanomoles/gram. N-acetyldopamine was not detected in human caudate nucleus, mouse whole brain, or liver from Rhesus monkey. When daily urinary excretion rates of N-acetyldopamine were determined in six individuals by both single-and dual-electrode electrochemical detection, the results were highly correlated for both free and total N-acetyldopamine (r>0.97,p<0.001). Using dual-electrode electrochemical detection, conjugated N-acetyldopamine accounted for 96.4% of the total N-acetyldopamine excretion. This value was 95.8% in the same individuals using single-electrode detection.