1.4.3.6) is a homodimer encoded by the AOC1 gene ( Barbry et al., 1990 Chassande et al., 1994), which is highly expressed in the intestine ( Wollin et al., 1998), the kidneys ( Schwelberger et al., 1998), and extravillous trophoblasts ( Velicky et al., 2018). The copper-containing amine oxidase human diamine oxidase (hDAO E.C. In severe anaphylaxis, mean histamine concentrations of 140 ng/mL have been measured ( van der Linden et al., 1992). Multiple potentially life-threatening conditions such as mast cell activation syndrome (MCAS) or anaphylaxis are accompanied by elevated histamine levels ( Valent et al., 2011). The development of hypotension strongly correlates with histamine concentrations ( Kaliner et al., 1982). It induces nitric oxide synthesis, which causes vasodilation, vascular hyperpermeability, edema formation, and consequently hypotension ( Ashina et al., 2015 Claesson-Welsh, 2015 Pober and Sessa, 2015 Valent et al., 2019). Following activation of the histamine receptors 1 and 2, histamine acts mainly on vascular endothelial, bronchial, and smooth muscle cells and causes symptoms affecting the cardiovascular system, the skin, and the gastrointestinal and respiratory tracts ( Jutel et al., 2009 Valent et al., 2011).

The biogenic amine histamine (2-ethylamine) is stored by basophils and mast cells (MCs) and is rapidly released after stimulation from intracellular storage vesicles.

Heparin half life