A THERMOCHEMICAL STUDY OF METABOLIC PATHWAYS IN ACTIVATED AND TRIGGERED 2C11-12 MOUSE MACROPHAGE HYBRIDOMA CELLS

Hybridization with lymphosarcoma cells immortalized mouse macrophages for the study of phagocytosis and cytobicidal properties. In the study of macrophage physiology, it became necessary to know more of their c ellular metabolism and the changes which occurred when the cells were triggered into the respiratory burst. It was found that, in common wit h many other types of growing cell, activated 2C11-12 macrophage hybri domas produced considerable lactate under fully aerobic conditions, ju dging from the highly exothermic CR ratio and subsequent spectrophotom etric analysis. Most of both the substrates (glucose and glutamine) wa s converted to lactate, respectively, by glycolysis and glutaminolysis , in the demand for biosynthetic precursors during growth. Glucose was the more important energy source. Approximately 60% of heat productio n was explained in terms of enthalpy changes in glucose and glutamine metabolism. It was suspected that fatty acid oxidation from contaminan ts in the bovine serum albumin needed for cell culture may be importan t in catabolism. The respiratory burst was triggered by phorbol-12-myr istate-13-acetate and recorded by greatly (5-fold) increased heat prod uction and enhanced chemiluminescence. Oxygen consumption was very rap id and soon led to anoxia in the closed culture system. The calorimetr ic-respirometric (CR) ratio was less negative and analysis confirmed t hat there was less lactate production. Radioisotope studies indicated that glycolysis and glutaminolysis were less intensive, with respirati on of glucose accounting for over 90% of the heat production. The impe rative for producing NADPH and cytotoxic oxygen metabolites heavily bi ased catabolism, reducing the supply of biosynthetic precursors. Known sources of heat production accounted for 87% enthalpy recovery and th e remainder may well be caused by fatty acid oxidation.