Inhibition of Histamine Formation in vivo

Abstract

QUANTITATIVE studies of the inhibition of histidine decarboxylase in vivo are now feasible with the introduction of two methods of assessing the rate of endogenous histamine formation in the rat. One method, devised by Schayer, measures the amount of ¹⁴C-histamine excreted in the urine following the injection of a known amount of ¹⁴C-histidine. The other method depends on the demonstration that in the female rat the urinary excretion of free histamine parallels the endogenous formation of the amine^1,2. Using both these methods, it was found that omitting pyridoxine from the diet for a week causes a reduction in histamine formation to about half normal, and that the rate of formation can be reduced further by superimposing injections of semicarbazide on the pyridoxine-deficient diet³.