Rhodamine 123 fluorescence of immortal hybridoma cell lines as a function of glucose concentration

The fluorescence of rhodamine 123 stained cells has been described to specifically reflect the activity of mitochondria. Changes in the intensity of fluorescence observed in stimulated lymphocytes were attributed to an increased glycolytic activity of cells due to increased growth rates. Previously reported changes in mitochondrial activity observed in batch cultures were likewise attributed to changed growth rates. In this study we report that the Rh123 fluorescence of hybridoma cell lines in batch culture more closely correlates to the glucose concentration in the culture supernatant than to growth rates. When cells are transferred into glutamine free medium with defined glucose concentrations ranging from 0 to 3,000 mg/L the mean Rh123 fluorescence adapts to the respective glucose concentration within 6 hours and gives a linear correlation. This can be explained by the previously described dependence of specific glucose consumption rates on glucose availability in the medium. The importance of controlling glucose availability, especially in large scale fermentations, is discussed.