Characterisation of taurine uptake in human KB MDR and non-MDR tumour cell lines in culture.

Studies on taurine transport in MDR (multidrug resistant) and non-MDR KB cancer cells show that both cell types contain Na(+)- and Cl(-)-dependent high-affinity and low-affinity transport systems selective for beta-amino acids and a taurine diffusion component. Good buffers, such as HEPES or MOPS, interfered with taurine uptake. The basal taurine Vmax measured in isoosmotic medium represented 1/5 of taurine captured by uptake in KB non-MDR, but was negligible in KB MDR cells. High-and low- affinity uptake systems were reduced by medium hyperosmolarity in both cell types. Although properties of low-and high-affinity transport systems were similar in both cell types, Vmax (but not Km) were reduced in MDR compared to non-MDR cells. Taurine uptake was unaffected by chemotherapeutic agents (doxorubicin, vinblastine) or MDR revertants (verapamil). Taurine did not affect cell proliferation of MDR or non-MDR cells nor did it alter the inhibitory effect of doxorubicin or vinblastine cell proliferation.