CADMIUM UPTAKE IN A SINGLE MDCK CELL EVID ENCED BY FURA-2 TITRATION -A FLUORESCENCE DIGITAL IMAGING STUDY

Cadmium influx rate in mammal kidney cells (MDCK) is analyzed using an original method based on fura-2 titration. The method relies on the h igh affinity of the fluorophore for the metal It follows that the exci tation spectrum shift of fura-2 can be linearly correlated to the infl ux rate of cadmium. Fluorescence digital imaging microscopy allows the study at single cell and intra-cellular organite levels. Results show that the cadmium uptake seems to be carrier dependent. Metal fluxes a re potential independent, with a temperature effect caracterized by a Q(10) of 2.3 +/- 0.2. No effect of verapamil is noticed however, cadmi um transport is inhibited by external calcium. Apparent dissociation c onstant for the cadmium uptake is estimated at 4.5 10(-5) M at 20 degr ees C. An additional passive transmembrane diffusion process is also e videnced.