Higher induction of histamine-forming enzyme, histidine decarboxylase, in various tissues in muramyldipeptide- and desmuramylpeptide-primed mice following intravenous injection of endotoxin

In mice, intravenous injection of two synthetic desmuramylpeptide (DMP) specimens, FK156 and FK565, definitely induced histidine decarboxylase (HDC) activity in the liver, spleen, and lungs, especially in the lungs, while muramyldipeptide (MDP) was scarcely active in this respect. These three components, especially FK565 followed by FK156, primed mice for enhanced induction of HDC activity in the organs upon challenge injection of synthetic endotoxin lipid A, where maximal activity was induced about 3 h after the injection of lipid A.