Immune cells glutamine utilised

In addition to synthesis, mnscle also stores glntamine. It is estimated that the total qnantity stored in aU the skeletal mnscles is about 80 g. The glutamine released by muscle can be utilised by the kidney, enterocytes in the small intestine, colonocytes, aU the immune cells and the cells in the bone marrow (Figure 8.24). Details of the pathways of utilisation by these tissues are discussed. 

The major tissues that use glutamine are kidney, small intestine, colon, immune cells and bone marrow cells. Rates of utilisation by these last four tissues cannot be measured in vivo. Rates of utilisation by isolated cells have been measured in vitro (Chapters 17 and 21). 

The physiological usefulness of this method for identifying the fuels that are used and their rates of utilisation in different cells is discussed in other chapters (Chapter 3). For example, measurement of the activity of the enzymes hexokinase and glutaminase in immune cells showed, for the first time, that glucose and glutamine are the major fuels utilised by these cells. This finding has had clinical significance (Chapter 17). 

The two fuels used by all immune cells are glucose and glutamine. Most of the glucose utihsed is converted to lactic acid and very little is oxidised i.e. ATP is generated from anaerobic glycolysis (see Chapter 6). Most of the glutamine utilised is converted to aspartate and very little is completely oxidised. This pathway is termed glutami-nolysis (see Chapters 8, 9 and 21). 

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