Enzymic histamine metabolism in guinea-pig skin and its role in immediate hypersensitivity reactions.

Incubation of histamine with guinea-pig skin or with a particle-free supernatant fraction of homogenized skin caused progressive temperature dependent decay of histamine activity. The loss of histamine activity was due to enzymic degradation of histamine by diamine oxidase since it was reversed by aminoguanidine. Burimamide caused a similar though less marked reversal of histamine degradation. Studies using S-adenosylmethionine, an essential cofactor of histamine-N-methyl transferase suggested the presence in a latent form in guinea-pig skin of a second pathway for enzymic degradation of histamine involving N-methylation. Pretreatment of guinea-pigs with aminoguanidine caused marked potentiation of the 72 hr homologous PCA reaction which suggests that histamine degradation is an important modulating factor in immediate allergic reaction in this species.