Functional Characterization of a High-Affinity Choline Transport System in Human Keratinocytes  Kathrin Hoffmann, Franziska Grafe, Wolfgang Wohlrab, Reinhard H. Neubert, Matthias Brandsch, Dr.  Journal of Investigative Dermatology  Volume 119, Issue 1, Pages 118-121 (July 2002) DOI: 10.1046/j.1523-1747.2002.01801.x Copyright © 2002 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 1 Time course of [3H]choline uptake in HaCaT cells. Uptake of [3H]choline (3 nM) was measured in buffer (pH 7.5) containing NaCl 140 mM (closed circles) or LiCl 140 mM (open circles). Data are shown as mean ± SEM, n ≥ 4. Journal of Investigative Dermatology 2002 119, 118-121DOI: (10.1046/j.1523-1747.2002.01801.x) Copyright © 2002 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 2 Effect of pH on [3H]choline uptake in HaCaT cells. Uptake of [3H]choline (3 nM) was measured in buffer with different pH values containing NaCl 140 mM for 10 min. Data are shown as mean ± SEM, n ≥ 4. Journal of Investigative Dermatology 2002 119, 118-121DOI: (10.1046/j.1523-1747.2002.01801.x) Copyright © 2002 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 3 Saturation kinetics of choline uptake in HaCaT cells. Uptake of [3H]choline (3 nM) in presence of increasing concentrations of unlabeled choline was measured at pH 7.5 for 10 min. The results are shown as mean ± SEM, n ≥ 4, after subtraction of the nonmediated component of transport ([3H]choline uptake in presence of 20 mM unlabeled choline). Inset: Eadie-Hofstee plot. Journal of Investigative Dermatology 2002 119, 118-121DOI: (10.1046/j.1523-1747.2002.01801.x) Copyright © 2002 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 4 Substrate specificity of [3H]choline uptake in HaCaT cells. Uptake was measured at pH 7.5 for 10 min. Concentration of inhibitors was 1 mM. Data are shown as mean ± SEM, n = 4. Journal of Investigative Dermatology 2002 119, 118-121DOI: (10.1046/j.1523-1747.2002.01801.x) Copyright © 2002 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 5 Dose–response relationship for the inhibition of [3H]choline uptake by various organic cations in HaCaT cells. Uptake of [3H]choline (3 nM) was measured in the absence (control) or presence of increasing concentrations of various organic cations at pH 7.5 for 10 min. The results are shown as mean ± SEM, n ≥ 4. Journal of Investigative Dermatology 2002 119, 118-121DOI: (10.1046/j.1523-1747.2002.01801.x) Copyright © 2002 The Society for Investigative Dermatology, Inc Terms and Conditions

Figure 6 Substrate specificity of choline uptake in normal keratinocytes. Uptake of [3H]choline was measured in the presence of various organic cations (1 mM) at pH 7.5 for 10 min. The results are shown as mean ± SEM, n ≥ 4. Journal of Investigative Dermatology 2002 119, 118-121DOI: (10.1046/j.1523-1747.2002.01801.x) Copyright © 2002 The Society for Investigative Dermatology, Inc Terms and Conditions