EFFECT OF TIME FACTOR ON THE NITROGEN SPARING EFFECT OF DIETARY CARBOHYDRATE

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Abstract
The effect of the time factor on the nitrogen sparing effect of dietary carbohydrate was studied in growing rats. During a 10-day feeding period no significant differences were observed in weight gains of rats receiving carbohydrate with the dietary protein (casein) or 8 h after protein was fed. Rats receiving carbohydrate with the protein retained significantly more nitrogen during the first day of the experiment than those receiving protein and carbohydrate separately, but this difference was not evident after the first day.Rats receiving casein alone had elevated plasma amino acid levels, which remained high until carbohydrate was fed 8 h later. The pattern of fall of the amino acids bore a resemblance to the pattern of amino acids in carcass protein.Rats fasted for 16 h had low levels of liver glycogen; when protein was given alone, some was utilized for glycogen formation. Carbohydrate, given 8 h after the protein, increased liver glycogen to normal levels and spared the protein fed at the next meal.