Regulation of dopamine uptake by basic fibroblast growth factor and epidermal growth factor in cultured rat...

We examined the characteristics of dopamine (DA) uptake and its regulation by neurotrophic factors such as basic fibroblast growth factor (bFGF) and epidermal growth factor (EGF) in cultured rat astrocytes. In the presence of inhibitors of monoamine oxidase (MAO) and catechol-O-methyl-transferase (COMT), astrocytes took up DA by Na(+)-dependent and Na(+)-independent mechanisms that were sensitive to a reduction in temperature. The Na(+)-dependent and Na(+)-independent components increased linearly with increasing [3H]DA concentration (1-1000 microM), and showed no saturation. Na(+)-dependent DA uptake was significantly inhibited by ouabain, a Na(+)-K+ ATPase inhibitor. In bFGF-treated astrocytes, [3H]DA uptake increased in a time-dependent manner until 48 h, and declined after 72 h in both the presence and absence of Na+. In EGF-treated astrocytes, [3H]DA uptake increased in a time-dependent manner until 72 h in both the presence and absence of Na +. This enhancement of DA uptake induced by EGF or bFGF was significantly inhibited when the cells were cultured with actinomycin D, cycloheximide, or brefeldin A. Actinomycin D and brefeldin A also significantly inhibited the basal uptake of [3H]DA into astrocytes. These results suggest the existence of Na(+)-dependent and Na(+)-independent DA uptake in cultured rat astrocytes, and that EGF or bFGF might stimulate the expression and translocation of the extraneuronal DA transporter.