Kinetic parameters of methamphetamine and metabolites determined from modeling the data in Fig. 4 and Supplemental Fig. 4

Models were chosen based on examination of Eadie-Hofstee plots. Methamphetamine was fit to a standard Michaelis-Menten equation. Amphetamine uptake kinetics was fit to a biphasic Michaelis-Menten equation (eq. 5). p-OHMA hOCT1- and hOCT3-mediated transport were fit to a standard Michaelis-Menten equation. Sigmoidal kinetics of hOCT2-mediated p-OHMA transport was obtained by fitting transporter-mediated uptake to the Michaelis-Menten equation with a Hill slope (eq. 5) for the substrate concentration and half-maximal transport concentration (K1/2 in place of Km). Results represent mean ± S.D. of three independent experiments each run in triplicate.

MethamphetaminehOCT22.09 ± 0.8849.7 ± 12.2NDND
AmphetaminehOCT20.830 ± 0.5534.6 ± 23.7534 ± 350853 ± 474
p-OHMAhOCT114.5 ± 8.7312 ± 163NANA
hOCT2K1/2: 31.8 ± 9.3; H: 1.64 ± 0.151780 ± 718NANA
hOCT353.3 ± 6.21290 ± 830NANA
  • NA, not applicable; ND, not determined (due to high diffusion).