Further studies on the histamine metabolism in the M-2 adenocarcinoma

Further studies of the histamine metabolism in the M-2 adenocarcinoma have shown that the tumor and the intestinal histidine decarboxylase should have similar conformations, since both enzymes exhibit superimposable curves of activity vs. pH as well as nearly identical 50% inhibitory concentrations for the specific inhibitor NSD-1015. It has also be found that the increase of the radioactivity uptake by the tumor nuclear fraction compared to the intestinal nuclear fraction after their incubation with 3H-histamine, may be due to qualitative differences between the nuclei, since endogenous contents of DNA and associated proteins were not significantly different. The specific binding of 3H-histamine to different purified DNAs demonstrated very dissimilar proportions of bound histamine, suggesting a possible interaction of histamine with DNA, similar to some of the proposed mechanisms for the modulation of the genomic expression of DNA by some polyamines.