Elevation of histamine levels in rat and mouse tissues by the deacetylation of administered N-acetylhistamine.

N-Acetylhistamine administered to mice and rats (200-800 mg/kg, i.p.) elevated tissue histamine levels to a considerable extent. N-Acetylhistamine was more potent to elevate histamine than was histidine, a precursor amino acid of histamine. From the present results and the distribution of N-acetylhistamine deacetylase in tissues, it could be concluded that the elevation of histamine was due to the deacetylation of N-acetylhistamine. In addition, a slight but significant amount of N-acetylhistamine was found in tissues of normal rats. The physiological role of the deacetylation of N-acetylhistamine is discussed on the basis of these results.