Simultaneous induction of histidine and ornithine decarboxylases and changes in their product amines following the injection of Escherichia coli lipopolysaccharide into mice.

The injection of Escherichia coli lipopolysaccharide (LPS) into mice produced simultaneous induction of histidine and ornithine decarboxylases in the liver, lung, spleen and kidney. The time courses of the changes in activities of the two enzymes were similar in all the tissues. After the injection, both activities increased within 1.5 hr, peaked at 4.5 hr and returned to the basal levels within 15 hr. The induction of these enzymes was very sensitive to this agent, i.e. as little as 1 microgram/kg of the E. coli lipopolysaccharide produced significant increases in these enzyme activities. An increase in the product amines, histamine and putrescine, followed the rise of enzyme activities. The levels of histamine changed more rapidly than those of putrescine. In spite of the increase in putrescine, there was no increase in spermidine and spermine. In the brain and thymus the LPS induced ornithine decarboxylase, but not histidine decarboxylase. In the blood, the histamine level increased without an increase in the activity of histidine decarboxylase. These results are discussed in relation to the actions of lipopolysaccharide. A simple method for the simultaneous assay of the activities of histidine and ornithine decarboxylases without using radioisotope substrates was used in this study.