We plan to determine the mechanism by which glutamine is transported from the cytoplasm to the mitochondrial matrix, where the glutaminase enzymes are located. The kinetics of transport will be examined in order to determine whether the amino acid crosses by diffusion or is transported by an active transport system (or by facilitated diffusion or exchange system). If the transport systems turns out to be carrier mediated then we plan to determine whether this system is under physiological control, i.e. does it increase or decrease in different physiological states that are known to lead to alterations in renal glutamine deamination and ammonia production. I plan to study the role of the purine-nucleotide cycle in the production of ammonia by skeletal muscle. In addition I plan to determine the contribution of glutamine synthesis by skeletal muscle to the supply of circulating glutamine. If the contribution turns out to be significant, I then plan to determine whether this synthetic process and ammonia production in skeletal muscle are altered during physiological states leading to increased or decreased renal glutamine deamination, e.g. alterations in acid-base balance.