Transport as Control Mechanism of Cerebral Metabolxite Levels

Abstract

The paper discusses the possible role that transport mechanisms of metabolites play in the nervous system. The chapter discusses about transport mechanisms controlling levels of amino acids at steady state. Relationships that bring attention to the idea that amino acid levels are functionally important in the nervous system appeared when the levels of cerebral amino acids in various species were compared. The table is also mentioned in the paper. It also has investigations on the amino acids present in higher levels in the brain like glutamic acid, taurine, aspartic acid, and GABA and of amino acids present in lower levels in the brain such as methionine, ornithine, and isoleucine. The close similarity of the patterns of amino acid concentration not only indicates the functional significance of such patterns but also indicates the existence of mechanisms that keep the composition of the cerebral amino acid pool at a constant pattern. Mechanisms determining amino acid levels in brain slices, Energy supply of cerebral transport, Comparison of cerebral amino acid levels in vivo with the uptake of amino acids by brain slices and alterations in cerebral amino acid transport and the cerebral amino acid pool are also mentioned in brief in the abstract. As a conclusion, the paper tells that the observations pointed out the possibility that those transport processes that can be observed in brain slices may have the determining role in controlling the levels of cerebral metabolites, especially since it is likely that uptake and exit determine the level of amino acids when brain slices are incubated in media containing amino-acids. It seems not only that influx and efflux determine the steady state level of amino acids in brain slices, but that any alteration in either flux will correspondingly alter the steady state levels. It has to be emphasized that not only influx, but also efflux, is an important determinant, and that the possibility exists that these two fluxes can be independently influenced.