Studies on histamine metabolism in intrinsic bronchial asthma.

Histamine metabolism was investigated in patients with intrinsic asthma, during the acute phase and in remission, by determination of the urinary excretion of histamine metabolites. During acute attacks the excretion of methylhistamine (MeHi) and 1-methyl-4-imidazoleacetic acid (MeImAA) was significantly increased compared with healthy subjects. The excretion of MeHi was significantly increased during acute attacks compared with remission. The excretion of MeImAA was also increased, but the difference was not significant. The correlation between the excretion of MeHi and MeImAA was highly significant. Corticosteroids, given to some patients during remission, did not affect the excretion of histamine and its metabolites. Smoking and respiratory infection during the acute attacks were both accompanied by increased excretion of MeHi. The results indicate that there is an increased histamine turnover in acute attacks of intrinsic bronchial asthma.