Liver ammonia transport from muscle

Glutamate is transported to liver mitochondria, where glutamate dehydrogenase liberates the amino group as ammonium ion (NHJ). Ammonia formed in other tissues is transported to the liver as the amide nitrogen of glutamine or, in transport from skeletal muscle, as the amino group of alanine. 

Tissue electrodes [2, 3, 4, 5, 45,57], In these biosensors, a thin layer of tissue is attached to the internal sensor. The enzymic reactions taking place in the tissue liberate products sensed by the internal sensor. In the glutamine electrode [5, 45], a thick layer (about 0.05 mm) of porcine liver is used and in the adenosine-5 -monophosphate electrode [4], a layer of rabbit muscle tissue. In both cases, the ammonia gas probe is the indicator electrode. Various types of enzyme, bacterial and tissue electrodes were compared [2]. In an adenosine electrode a mixture of cells obtained from the outer (mucosal) side of a mouse small intestine was used [3j. The stability of all these electrodes increases in the presence of sodium azide in the solution that prevents bacterial decomposition of the tissue. In an electrode specific for the antidiuretic hormone [57], toad bladder is placed over the membrane of a sodium-sensitive glass electrode. In the presence of the antidiuretic hormone, sodium ions are transported through the bladder and the sodium electrode response depends on the hormone concentration. 

Alanine Transports Ammonia from Skeletal Muscles to the Liver... 

The use of alanine to transport ammonia from skeletal muscles to the liver is another example of the intrinsic economy of living organisms. Vigorously contracting skeletal muscles operate anaerobically, producing pyruvate and lactate from glycolysis as well as... 

More Than One Carrier Exists for Transporting Ammonia from the Muscle to the Liver Amino Acid Catabolism Can Serve as a Major Source of Carbon Skeletons and Energy For Many Genetic Diseases the Defect Is in Amino Acid Catabolism... 

Urea is the form in which amino groups derived from amino acids are disposed of from the body. One nitrogen atom of the urea molecule comes from free ammonia, the other from aspartate. All but two of the reactions of the cycle occur in the cytosol of liver hepatocytes the other two occur in the mitochondria. Urea is transported to the kidney for excretion into the urine. Urea is produced by the liver even during starvation, as skeletal muscle proteins are broken down to release amino acids to act as gluconeogenic precursors. The amino group is removed from these amino acids and converted into urea, which is then excreted in the urine. 

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