Question

Rats were fasted overnight and then given a single meal that was low in carbohydrate and high in protein content. The meal contained all amino acids except arginine, which is an essential amino acid. Within 2 hours, blood ammonia levels rose by 800%. A control group of rats were fasted and then fed the same low carb and high protein meal but with arginine included. This latter group showed no change in blood ammonia levels.

Fasting was required to obtain this difference in blood ammonia levels. Why?

What caused the ammonia level to rise in the experimental group compared to the control group?

Answer 1

Ans - In case of fasting, it lowers blood glucose levels. Giving a arginine free diet resulted in rapid breaks down molecules into smaller units(catabolism) of all the amino acids present. And due to lack of essential amino acids this catabolism was even faster and worse because protein synthesis was not performed due to lack of essential amino acids.

Oxidative deamination of amino acids is the main reason behind rise in ammonia level of rats. And further lack of arginine slowed the conversion of ammonia to urea.