The present work has examined the ability of human, canine and rat renal tissues to synthesize dopamine from added L-3,4-dihydroxyphenylalanine (L-DOPA); the deamination of newly-formed dopamine into 3,4-dihydroxyphenylacetic acid (DOPAC) was also studied. In some experiments, slices of renal cortex obtained from the human, dog and rat kidneys were used; tissues were incubated with increasing concentrations (5-5000 microM) of L-DOPA. The accumulation of newly-formed dopamine was, in all three species, found to be dependent on the concentration of L-DOPA, being the rat renal tissues endowed with a greater ability to produce dopamine, followed by the human and the dog tissues. In experiments performed in kidney homogenates, the decarboxylation of L-DOPA into dopamine was also found to be dependent, in all three species, on the concentration of L-DOPA used (10-5000 microM). AAAD activity as determined in kidney homogenates was found to be in the rat kidney (Vmax = 7.7 +/- 0.8 nmol mg-1 protein h-1) higher than that occurring in the human (Vmax = 5.8 +/- 0.6 nmol mg-1 protein h-1) and the dog kidney (Vmax = 3.9 +/- 0.5 nmol mg-1 protein h-1). No statistically significant differences were found between the Km values of the three species (human, 62 +/- 8 microM; dog, 54 +/- 6 microM; rat, 82 +/- 12 microM). A considerable amount of newly-formed dopamine in both kidney slices and homogenates was converted into DOPAC; the DOPAC/dopamine ratios in these experimental conditions were greater in the human kidney, followed by the rat and dog.(ABSTRACT TRUNCATED AT 250 WORDS)