Figure 5.

Transport measurements from apical and basolateral surfaces of cell monolayers. MDCK cells expressing DAT, NET, and the chimeric and deletion constructs were incubated for 8 min with [³H]DA added to either the apical side or the basolateral side of the cell monolayer. The amount of [³H]DA accumulated in the cells from each side are compared and shown as a relative percentage with the sum of the DA accumulation from both sides as 100%. The open bars and filled bars represent DA accumulation from the apical and basolateral sides, respectively. The transporter constructs expressed are indicated under the bars. The experiments were performed in triplicate, and the data shown are from representative experiments. SDs are shown as error bars. The absolute value of DA transport (100%) varied from 7.2 to 13.6 pmol/min/mg protein except for mutants m4, m5, and m6. Many of the cell lines were not clonal and represented a mixture of transfected and nontransfected cells. The 100% values for m4, m5, and m6 were 0.12, 5.4, and 5.6 pmol/min/mg protein, respectively, which was in approximate agreement with the percentage of transfected cells in the population.