title: A comparative study on the synthesis of dopamine in the human, dog and rat kidney.
abstract: 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)
authors.affiliation: Department of Pharmacology & Therapeutics, Faculty of Medicine, Porto, Portugal.
authors.forename: P
authors.initials: P
authors.lastname: Soares-da-Silva
authors.forename: M H
authors.initials: MH
authors.lastname: Fernandes
authors.forename: M
authors.initials: M
authors.lastname: Pestana
mesh_terms: D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism; D000818:Animals; D001142:Aromatic-L-Amino-Acid Decarboxylases / Q000378:metabolism; D003653:Decarboxylation; D004285:Dogs; D004298:Dopamine / Q000096:biosynthesis*; D006801:Humans; D066298:In Vitro Techniques; D007668:Kidney / Q000201:enzymology / Q000378:metabolism*; D007672:Kidney Cortex / Q000378:metabolism; D007700:Kinetics; D007980:Levodopa / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D051381:Rats; D017208:Rats, Wistar
chemical_list: D015102:3,4-Dihydroxyphenylacetic Acid; D007980:Levodopa; D001142:Aromatic-L-Amino-Acid Decarboxylases; D004298:Dopamine