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Starvation and Refeeding: Effects on the Periodicity of Tryptophan and Tyrosine Metabolism in Mice

Biochemistry and Pharmacology Laboratory, U. S. Army Research Institute of Environmental Mediicne, Natick, Massachusetts 01760

Starvation of mice for 48 hours results in increased specific activity of hepatic tryptophan oxygenase, while refeeding promptly decreases these levels. Alternatively, while food deprivation has variable effects upon the activity of tyrosine aminotransferase, within 2 hours after refeeding there occurs a sharp elevation in the activity of this enzyme. After 12 hours of food deprivation, plasma levels of tyrosine and tryptophan are sharply reduced, but increase between 12 and 48 hours probably as a result of amino acid mobilization and protein degradation. Upon refeeding, plasma levels of both these amino acids increase rapidly. While tryptophan concentrations return to control values between 24 and 48 hours of refeeding, the elevated tyrosine levels persist throughout the 48-hour period.

KEY WORDS: • starvation • refeeding • tyrosine • tryptophan • tyrosine aminotransferase • tryptophan oxygenase • periodicity

Manuscript received 18 October 1971.