Fig. 3.

Saturation analysis of dopamine uptake and RTI-55 binding in primary cultures. Representative data of dopamine uptake (A) and RTI-55 binding (B) obtained in parallel cultures are presented. Data are averages of duplicate observations. The V_max of dopamine uptake is 10 pmol/well for 2 min, and theB_max of RTI-55 binding is 88 fmol/well. The DAT turnover rate calculated from this experiment is 0.95/sec (83.3/88 fmol per second), with an average of 0.74 ± 0.07/sec from four independent experiments. Affinity of RTI-55 binding in cultures is 1.8 ± 0.5 nm. A total of nine independent experiments (including those used for turnover rate estimation and control groups from subsequent experiments) were used to determine K_m of dopamine uptake at 560 ± 60 nm.