“…3 shows two methylhistamines that could, in principle, be formed by metabolism: tele-methylhistamine, also named Nr-methylhistamine (i.e., t-MH) and pros-methylhistamine or N~-methylhistamine (i.e., p-MH). t-MH is by far the dominant methylated metabolite formed (see Schayer, 1978;Wetterqvist, 1978;Beaven, 1982;Code, 1985). Endogenous t-MH has been found in human body fluids (see Keyzer etal., 1981;Swahn and Sedvall, 1981;Kahndelwal etal., 1982a;Imamura etal., 1984b) and in tissues (Green, 1970;Hough etal., 1979Hough etal., , 1981Oishi et al, 1984;Imamura et al, 1984b).…”