Some Aspects of Acid-Base Metabolism in the Immature Central Nervous System
Tissue acid-base metabolism is an important, but often neglected, area of investigation for several reasons. In the first place, the millieu in which cellular enzymatic reactions occur and in which many drug effects are exerted is intracellular fluid rather than extracellular fluid or blood. Second, tissue pH affects drug distribution, particularly if the drugs are weak electrolytes and non-ionic diffusion is an important determinant of their tissue-plasma ratios. Third, the processes, both active and passive, that are responsible for cellular hydrogen ion homeostasis are perhaps closely linked with other cellular activities of demonstrated significance, e.g., sodium transport. Finally, in the central nervous system (CNS), tissue acid-base balance is intimately related to cerebrospinal fluid (CSF) acid-base parameters and their regulation. Thus, it is appropriate to include a discussion of CNS and CSF acid-base metabolism in a symposium concerned with drug effects and distribution in the developing nervous system. There are, however, few data available concerned with acid-base regulation in the immature CNS and CSF. The purpose of this report is to summarize this information, and, more importantly, to point out what is not known about CNS acid-base balance in the immature animal. It is hoped that the questions not answered, and, in some cases not even directly proposed, will serve as a stimulus for more inquiry in this special research area.
KeywordsBiochemical Development Immature Animal Carbonic Anhydrase Activity Fetal Lamb Immature Central Nervous System
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