ARS | Publication request: Arginine utilization of citrulline synthesis in arginase II knockout mice

Submitted to: Journal of Federation of American Societies for Experimental Biology
Publication Type: Abstract Only
Publication Acceptance Date: February 1, 2010
Publication Date: April 6, 2010
Citation: Marini, J.C., Didelija, I.C., Castillo, L., Lee, B. 2010. Arginine utilization of citrulline synthesis in arginase II knockout mice [abstract]. Federation of American Societies for Experimental Biology 24:740.15.

Technical Abstract: The synthesis of citrulline (Cit) from arginine (Arg) in the small intestine depends on the activity of arginase II (ARG2). To test the hypothesis that Arg is the main dietary precursor for Cit synthesis, despite the lack of ARG2, tracer studies were conducted in WT and ARG2 ko conscious mice. WT mice had a higher rate of appearance (Ra) of Cit (130 vs. 118 µmol/kg–1 /h–1) than ARG2 ko mice, but no difference in Ra of ornithine (Orn; 278 µmol/kg–1 /h–1) was observed. There were significant differences in the utilization of dietary Cit precursors. The contribution of dietary Arg to the synthesis of Cit was reduced from 44 to 11 µmol/kg–1 / h–1 due to the lack of ARG2. No arginine was utilized at the site of Cit synthesis in ARG2 ko mice (WT = 26 µmol/kg–1 / h–1) and the contribution of Arg through Orn was reduced (18 vs. 14 µmol/kg–1 / h–1). Pro and Gln utilization increased in ARG2 ko mice from 5.7 to 8.1, and 0.7 to 1.9 µmol/kg–1/ h–1, respectively. Most of the contribution of Pro and Gln was at the site of Cit synthesis, rather than through plasma Orn. Arg is still the main dietary precursor for Cit synthesis, despite the lack of ARG2 at the site of Cit synthesis. Arg is converted to Orn elsewhere in the body, presumably by action of ARG1, and then utilized for Cit synthesis. The contribution of dietary Gln and Pro increased in ARG2 ko mice, but these amino acids are minor sources for Cit synthesis.