期刊
AMERICAN JOURNAL OF PHYSIOLOGY-ENDOCRINOLOGY AND METABOLISM
卷 298, 期 6, 页码 E1219-E1225出版社
AMER PHYSIOLOGICAL SOC
DOI: 10.1152/ajpendo.00028.2010
关键词
kidney; mitochondria; glutaminase; 2-aminobicyclo[2,2,1]heptane-2-carboxylic acid
资金
- International Glutamate Technical Committee
- Canadian Institutes for Health Research
Treberg JR, Clow KA, Greene KA, Brosnan ME, Brosnan JT. Systemic activation of glutamate dehydrogenase increases renal ammoniagenesis: implications for the hyperinsulinism/hyperammonemia syndrome. Am J Physiol Endocrinol Metab 298: E1219-E1225, 2010. First published March 23, 2010; doi:10.1152/ajpendo.00028.2010.-The hyperinsulism/hyperammonemia (HI/HA) syndrome is caused by glutamate dehydrogenase (GDH) gain-of-function mutations that reduce the inhibition by GTP, consequently increasing the activity of GDH in vivo. The source of the hyperammonemia in the HI/HA syndrome remains unclear. We examined the effect of systemic activation of GDH on ammonia metabolism in the rat. 2-Aminobicyclo[2,2,1]heptane-2-carboxylic acid (BCH) is a nonmetabolizable analog of the natural GDH allosteric activator leucine. A dose of 100 mu mol BCH/100 g rat resulted in a mild systemic hyperammonemia. Using arterial-venous (A-V) differences, we exclude the liver, intestine, and skeletal muscle as major contributors to this BCH-induced hyperammonemia. However, renal ammonia output increased, as demonstrated by an increase in A-V difference for ammonia across the kidney in BCH-treated animals. Isolated renal cortical tubules incubated with BCH increased the rate of ammoniagenesis from glutamine by 40%. The flux through GDH increased more than twofold when BCH was added to renal mitochondria respiring on glutamine. The flux through glutaminase was not affected by BCH, whereas glutamate-oxaloacetate transaminase flux decreased when normalized to glutaminase flux. These data show that increased renal ammoniagenesis due to activation of GDH can explain the BCH-induced hyperammonemia. These results are discussed in relation to the organ source of the ammonia in the HI/HA syndrome as well as the role of GDH in regulating renal ammoniagenesis.
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