Glucose Diffusion Coefficients Determined from Concentration Profiles in Emt6 Tumor Spheroids Incubated in Radioactively Labeled L-Glucose

Abstract

In order to theoretically assess tissue energetic status, conditions for substance exchange need to be known. One group of parameters important in this context are diffusion coefficients of nutrients and metabolic waste products which may be assessed by incubating spheroids in a medium containing tracer amounts of the radioactively labeled substance in question, for a defined period of time. In previous studies, the overall amount of ¹⁴C-labeled substance taken up by the spheroids was measured by scintillation counters (e.g.[1]), or the concentration of ³H-labeled substance in the spheroid center was determined by autoradiography and grain counting (e.g. [4]). From a number of such measurements, diffusion coefficients may then be obtained using mathematical models. The information content of an autoradiogram can be exploited more efficiently by recording not only central grain density but rather grain density distributions from each of which a diffusion coefficient may be calculated. This can be done by grain counting on a radial track through an autoradiogram of a central spheroid section for ³ H labels or by measuring optical density (densitometry) in autoradiograms of central spheroid sections for ¹⁴ C labels.