Compartmentation of glutamate metabolism in brain. Evidence for the existence of two different tricarboxylic acid cycles in brain.
1. (14)C from [1-(14)C]glucose injected intraperitoneally into mice is incorporated into glutamate, aspartate and glutamine in the brain to a much greater extent than (14)C from [2-(14)C]glucose. This difference for [1-(14)C]glucose and [2-(14)C]glucose increases with time. The amount of (14)C in C-1 of glutamate increases steadily with time with both precursors. It is suggested that a large part of the glutamate and aspartate pools in brain are in close contact with intermediates of a fast-turning tricarboxylic acid cycle. 2. (14)C from [1-(14)C]acetate and [2-(14)C]acetate is incorporated to a much larger extent into glutamine than into glutamate. An examination of the time-course of (14)C incorporated into glutamine and glutamate reveals that glutamine is not formed from the glutamate pool, labelled extensively by glucose, but from a small glutamate pool. This small glutamate pool is not derived from an intermediate of a fast-turning tricarboxylic acid cycle. 3. It is proposed that two different tricarboxylic acid cycles exist in brain.
D000085:Acetates / Q000378:metabolism; D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism; D001921:Brain / Q000378:metabolism*; D002247:Carbon Isotopes; D002952:Citric Acid Cycle; D005947:Glucose / Q000378:metabolism; D005971:Glutamates / Q000378:metabolism*; D005973:Glutamine / Q000378:metabolism; D051379:Mice; D008956:Models, Chemical
D000085:Acetates; D002247:Carbon Isotopes; D005971:Glutamates; D005973:Glutamine; D001224:Aspartic Acid; D005947:Glucose