An unconscious patient was delivered by ambulance to the hospital. On objective examination the patient was found to present no reflexes, periodical convulsions, irregular breathing. After laboratory examination the patient was diagnosed wi- th hepatic coma. Disorders of the central nervous system develop due to accumulation of the following metabolite:

Answer options

1. Urea
2. Glutamine
3. Histamine
4. Ammonia
5. Bilirubin

Explanation

The ammonia accumulates in the brain tissues, some of which is converted to glutamine, by way of the glutamine synthetase pathways, leading to localized swelling of astrocytes (brain cells). This ammonia-induced glutamine accumulation may cause dysfunction of astrocytes that leads to impairment of vascular reactivity.