A researcher is working with dogs. Overnight, the dogs were fasted then the foll

Question

A researcher is working with dogs. Overnight, the dogs were fasted then the following day fed a diet complete with all amino acids minus Arg. In two hours, the dog’s blood ammonia levels spiked from 21 ug/mL (prior to feeding) to 159 ug/mL after feeding. Control dogs fed a meal complete with arginine showed no effects. Answer the following questions: a. Why did the researcher fast the animals? b. Why did the ammonia levels spike? c. Suppose you were to feed the dogs another amino acid other than arginine that would allow ammonia levels to remain constant after fasting. Which amino acid would that be and why?

Explanation / Answer

A. To check the toxicity crated by ammonia when the arginine which is an essential amino acid is not given in the diet and to check whether arginine is essential amino acid or not.

B. Ammonia level rise due to the process of oxidative deamination. Arginine which is an essential amino acid is also an intermediate in the urea cycle. Thus in its absence the conversion of formed ammonia to urea will be slowed down.

C. Ornithine or citrulline can be used here as this amino acid is also an intermediate of the pathway which converts ammonia into urea or the urea cycle.

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