Uptake of Rhodamine 123 in H-FT–transfected clones. Role of temperature. Uptake of Rhodamine 123 (5 μmol/L in a buffered salt solution) into 10⁶/mL cells was performed at the two indicated temperatures. At different times aliquots were transferred to an ice-cold buffered salt solution, and samples were aliquoted for FACS analysis (10⁴ cells per sample). The median fluorescence values (given as arbitrary units, au) are plotted as a function of time (of n = 3 representative experiments).