Total | es | ei | ||||
---|---|---|---|---|---|---|
Max | Vi | Max | Vi | Intracellular Concentration at 5 Min | Vi | |
μM | pmol/μl/s | μM | pmol/μl/s | μM | pmol/μl/s | |
HN-5a | ||||||
−Na | 14.3 ± 0.9 | 0.53 ± 0.04 | 15.0 ± 1.4 | 0.48 ± 0.07 | 5.8 ± 0.5 | 0.05 ± 0.01 |
+Na | 14.5 ± 0.4 | 0.75 ± 0.061-a | 12.4 ± 0.8 | 0.71 ± 0.07 | 6.7 ± 0.4 | 0.03 ± 0.01 |
GEM-8e | ||||||
−Na | 14.0 ± 0.6 | 0.99 ± 0.051-b | 13.3 ± 0.5 | 0.89 ± 0.051-b | 6.8 ± 0.6 | 0.04 ± 0.01 |
+Na | 13.1 ± 0.5 | 0.90 ± 0.11 | 12.4 ± 0.8 | 0.87 ± 0.15 | 5.8 ± 0.7 | 0.05 ± 0.01 |
Cells were incubated with 10 μM [3H]formycin B in presence and absence of 100 nM NBMPR or 10 μM NBMPR/dipyridamole for various times as shown in Fig. 3. Cells were equilibrated in either normal Dulbecco’s PBS (+Na) or in an Na+-free buffer (−Na; iso-osmotic replacement with Li+). Total transporter-mediated uptake (Total) was defined as that sensitive to inhibition by 10 μM NBMPR/dipyridamole. NBMPR-sensitive uptake (es) was calculated as difference between uptake in presence and absence of 100 nM NBMPR, whereas NBMPR-resistant uptake (ei) was defined as difference between uptake in presence of 100 nM NBMPR and that observed in the presence of 10 μM NBMPR/dipyridamole. Hyperbolic curves were fitted to resulting time course data and extrapolated to obtain estimates of initial rate of influx (Vi) and, for total and es-mediated components, steady-state intracellular concentrations of [3H]formycin B (Max); forei-mediated uptake, which did not approach steady state over time course of these assays, intracellular concentration after 5-min incubation is shown. Each value represents mean ± S.E. of four independent experiments.