Mammalian nitrate biosynthesis: incorporation of 15NH3 into nitrate is enhanced by endotoxin treatment.

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Abstract
Incorporation of an oral dose of [15N]ammonium acetate into urinary [15N]nitrate was demonstrated in the rat. Investigation of the regulation of nitrate synthesis showed that Escherichia coli lipopolysaccharide potently stimulates urinary nitrate excretion (9-fold increase). The enhanced rate of nitrate excretion by lipopolysaccharide was due not to a reduction in nitrate metabolic loss but rather to an increased rate of synthesis. This conclusion was based on finding a proportionally increased incorporation of [15N]ammonium into nitrate nitrogen with lipopolysaccharide treatment. Nitrate biosynthesis was also increased by i.p. injection of carrageenan and s.c. injection of turpentine. The pathway of nitrate biosynthesis may be the result of oxidation of reduced [carcinogenic] nitrogen compounds by oxygen radicals generated by an activated RES. Rats exposed to E. coli lipopolysaccharide, which results in an endotoxin-induced fever, have an enhanced nitrate biosynthesis.