DEVELOPMENTS IN CELLULAR MICROCALORIMETRY WITH PARTICULAR EMPHASIS ONTHE VALUABLE ROLE OF THE ENERGY (ENTHALPY) BALANCE METHOD

This review of microcalorimetric studies of animal cells includes musc le and nerve as well as blood tissue, non-erythroid cells and transfor med cells. It highlights the wide range of heat flow rate (phi = dQ/dt ) data obtained for cells but points to their limited inherent value u nless expressed per unit volume or biomass-scalar heat flux. Measureme nts of heat flow have been used in detecting clinical, pharmacological , toxicological and immunological changes-calorimetry as an analytical tool to assay metabolic activity in the face of pathological and xeno biosis-induced alterations. Microcalorimetry is a powerful and non-des tructive technique of itself but its true strength is revealed when co mbined with other analytical procedures to allow access to the energy (enthalpy) balance method, which has its basis in the First Law of The rmodynamics. Its early use in dissecting all the chemical sources of h eat in the thermogenesis of muscle is summarized, together with more r ecent studies of the metabolic burst in phagocytosis and catalytic pat hways in cultured, anchorage-independent T-lymphoma and LS-L929 mouse fibroblasts. The theoretical basis of the calorimetric-respirometric ( CR) ratio is explained and its value in detecting anaerobic pathways i n respiring cells is emphasized with reference to several cell types. Two ways of calculating ATP turnover (mumol infinity ATP h-1) are desc ribed, namely from heat flow and catabolic coupling flow; and there is opuscular reference to thermodynamic efficiency.