GEOGRAPHICAL MAPPING OF METABOLITES IN BIOLOGICAL TISSUE WITH QUANTITATIVE BIOLUMINESCENCE AND SINGLE-PHOTON IMAGING

This article features a novel technique for measuring the spatial dist ribution of metabolites, such as ATP, glucose, and lactate, in rapidly frozen tissue. Concentration values are obtained in absolute terms an d with a spatial resolution of single-cell dimension. The method is ba sed on enzymatic reactions that link the metabolite of interest to luc iferase with subsequent light emission. Using a specific array, cryose ctions are brought into contact with the enzymes in a well-defined, re producible way inducing a distribution of light across the section wit h an intensity that is proportional to the metabolite concentration. T he emitted light can be visualized through a microscope and an imaging photon counting system, and the respective image can be transferred t o a computer for image analysis. Measurements in spherical cell aggreg ates with central necrosis demonstrate a close correlation between the distribution of ATP and of cellular viability at a microregional leve l. Similarly, ATP and glucose are correlated with the geometrical arra ngement of more viable and more necrotic tissue regions in human melan omas xenografted in nude mice. Lactate did not show such a structure-r elated distribution in these tumours. Structure-related distributions of ATP, glucose, and lactate are found in cervix tumours of patients. In contrast to the heterogeneous distributions in tumours, the distrib ution patterns were much more homogeneous in normal tissues. Regional differences were present, but were much more gradual than in malignanc ies. This was illustrated for heart muscle where ATP concentrations we re found that agreed with data in the literature, and that showed a de crease in periventricular areas.