Increase in plasma ammonia and amino acids when rats are fed a 44% casein diet

B. A. Semon, P. M.B. Leung, Quinton Rogers, D. W. Gietzen

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6 Scopus citations


Rats were trained to eat a 6% casein basal diet during a 3-hour period per day. They were then fed either the same 6% casein diet or a 44% casein diet for 3 hours. No food intake depression was observed in the rats eating 44% casein diet during the 3-hour period. Plasma ammonia and amino acids and brain amino acids were measured at 0, 4, 12 and 24 hours after presentation of the 6% or 44% casein diets. Plasma ammonia rose to 134 (p<0.01) and 110 micromolar (p<0.05) in the 44% casein fed rats at 4 and 12 hours, respectively, as compared to 67 and 53 micromolar, respectively, for the 6% casein fed rats. All plasma amino acid concentrations except methionine and glutamate were elevated (p<0.05) at 4 hours. In the brain, threonine, glutamine and tyrosine concentrations were elevated (p<0.05) at 4 hours after diet presentation. At 24 hours, valine, isoleucine, leucine, phenylalanine, and methionine concentrations were also elevated (p<0.05). Because intake of the 44% casein diet decreases the second day of its presentation, as noted in an earlier experiment, the increases in plasma ammonia and its possible entry into the brain as reflected by increased brain glutamine together with changes in amino acid concentrations should be considered collectively among possible metabolic signals affecting intake of high protein diets.

Original languageEnglish (US)
Pages (from-to)631-636
Number of pages6
JournalPhysiology and Behavior
Issue number5
StatePublished - Jan 1 1988


  • Brain amino acids
  • Caloric Intake
  • Casein
  • High protein
  • Plasma amino acids
  • Plasma ammonia

ASJC Scopus subject areas

  • Experimental and Cognitive Psychology
  • Behavioral Neuroscience


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