Table 1

Characteristics of the ionic dependence of the [3H]dopamine uptake operated by hDAT, hNET, and six chimeric transporters.

TransporterClNa+NaCl
KmVmaxHill numberKmVmaxHill numberSC50VmaxHill number
mM mM mM
hDAT1234 53  ± 121-b 6.65  ± 1.10.84  ± 0.0658  ± 72.8  ± 0.62.45  ± 0.251-d 1-e 127  ± 5410.7  ± 3.01.66  ± 0.171-f 1-g
hNET 123427  ± 31-a 6.3  ± 0.70.82  ± 0.20100  ± 493.0  ± 1.551.31  ± 0.2278  ± 1717.4  ± 4.81.72  ± 0.381-f 1-g
A 1234 71  ± 71-a 6.4  ± 2.20.97  ± 0.1079  ± 351.3  ± 0.51.28  ± 0.321-e 79  ± 192.6  ± 1.01.90  ± 0.281-f 1-g
B123426  ± 96.3  ± 1.90.55  ± 0.0580  ± 141.2  ± 0.31.95  ± 0.261-d 88  ± 185.7  ± 0.11.60  ± 0.201-f 1-g
F123424  ± 31-b 1-c 0.5  ± 0.11.12  ± 0.1660  ± 184.4  ± 1.81.61  ± 0.251-d 26  ± 35.0  ± 1.11.39  ± 0.271-f 1-g
G1234 58  ± 290.05  ± 0.020.90  ± 0.2684  ± 20.1  ± 0.14.69  ± 1.5591  ± 140.1  ± 0.033.65  ± 2.60
J 123424  ± 31-a 1-c 0.2  ± 0.11.71  ± 0.9030  ± 180.4  ± 0.10.92  ± 0.2664  ± 261.51  ± 0.51.06  ± 0.231-f 1-g
L12348.6  ± 0.21-c 0.1  ± 0.051.35  ± 0.59215  ± 480.9  ± 0.67.17  ± 5.16198  ± 702.7  ± 1.351.48  ± 0.30

Cl ions contained in the Krebs Ringer medium were substituted by equimolar concentrations of isethionate (Cl experiments), whereas Na+ and NaCl contained in PBS were substituted with equimolar concentrations of Tris+ (Na+ experiments) or twice-equimolar concentrations of sucrose (NaCl experiments). Data are means ± S.E.M. of three to six estimates of K mfor ions and V max of uptake calculated using either Origin (Na+; Cl) or Ligand (NaCl) analysis software from data exposed in Fig. 2 and 3. V max values are expressed as picomoles of [3H]dopamine per 106 cells per minute. For NaCl experiments, we calculated an SC50 value that corresponds to the NaCl concentration that half-maximally stimulated the dopamine uptake.

    • 1-a  No significant difference for the exchange of cassette I in A/hDAT, hNET/B, and J/F, with (F(1,17) = 0.98).

    • 1-b  No significant difference for the exchange of cassette II in hDAT/G and F/L, with (F(1,13) = 0.06).

    • 1-cP < .01 for the exchange of cassette IV in F/hDAT, J/A, and L/G, with (F(1,18) = 8.35).

    • 1-dP < .001 for the exchange of cassette I in hDAT/A, B/hNET, and F/J, with (F(1,16) = 15.7).

    • 1-eP < .01 for the exchange of cassette IV in hDAT/F and A/J, with (F(1,10) = 5.6); the effect of the exchange of cassette IV was higher for hDAT/F than for A/J (F(1,10) = 12.6, P < .01).

    • 1-fP < .05 compared with Hill values in Tris substitution for hDAT, B, and F, with F(1,15) = 4.75; no significant difference with Hill values in Tris substitution for hNET, A, and J, with F(1,16) = 3.33 (P = .088).

    • 1-g  No significant difference with Hill values in Tris substitution for hDAT, A, and hNET, B, F, and J, with F(1,38) = 0.007.