Extensive conjugation of dopamine (3,4-dihydroxyphenethylamine) metabolites in cultured human skin fibroblasts and rat hepatoma cells

Abstract
[G-3H]Dopamine metabolism in human skin fibroblasts and rat hepatoma cells in culture was determined by high-pressure liquid-chromatographic analysis of both cell extract and uptake medium. Conjugated metabolites were selectively hydrolyzed by incubation with arylsulfatase [EC 3.1.6.1] or .beta.-glucuronidase before analysis. The principal metabolites of dopamine in fibroblast cells are 3-methoxytyramine 4-O-sulfate and 3-methoxytyramine. No significant differences, either in the amounts of these metabolites or in the amount of dopamine metabolism, were observed in fibroblasts from both normal and homocystinuric individuals. In rat hepatoma cells, the major metabolite of dopamine was 3-methoxytyramine 4- or 3-O-glucuronide; lower concentrations of dopamine 4- or 3-O-glucuronide, 4-hydroxy-3-methoxyphenylacetic acid, 3,4-dihydroxyphenylacetic acid and 2 unidentified glucuronide conjugates were also observed. Significant differences in the relative concentrations of these metabolites in cell and uptake medium were observed in both cell systems.