Glucose levels and succinate and lactate dehydrogenase activity in EMT6/Ro tumor spheroids

To evaluate the effects of glucose on the development of cell heterogeneity and the occurrence of necrotic areas in the center of tumor spheroids, a procedure (combining microdissection of small tissue samples from frozen-dried cryosections and microchemical analysis) was developed to measure glucose in distinct, concentrically arranged, microregions of tumor spheroids: the outermost area of proliferating cells, the area of nonproliferating cells and 2 central "necrotic" areas, with either abundant or little intercellular space. Since glucose levels, for analytical reasons, had to be expressed on a dry weight basis, and because of the morphological heterogeneity of the microregions of tumor spheroids, it was necessary to measure and take into account the regional differences in cell density (water content), in order to obtain adequate estimates of the glucose levels in the various microregions. At glucose concentrations of 5.5 and 3.6 mM in the culture medium, the glucose levels varied between 3.5 and 1.4 mmoles/kg wet weight and were lowest in those central areas where the cell density was lowest. Histochemical demonstration of the distribution of lactate and succinate dehydrogenase activity indicates a considerably higher capacity of tumor cells for anaerobic than for aerobic energy production.