In vivo Degradation of Histamine-adenine Dinucleotide Phosphate to Histamine Ribonucleoside

ENZYME-CATALYSED interactions of histamine with pyridine coenzymes, leading to formation of histamine-substituted dinucleotides, were previously observed in our laboratory 1–3 . These findings were later confirmed by Muraoka et al. 4,5 and Devi et al. 6 . In more recent experiments, 2 14 C (ring)-labelled histamine was administered to guinea pigs 7 , or it was incubated with mast cell preparations 8 and guinea pig lung mitochondria 9 . In all experimental set-ups, after deproteinization of the homogenized carcass or the incubation mixtures, carrier (non-labelled) histamine dinucleotides were added to the supernatant. After re-isolation and repeated (up to 15 times) purification by alternative ionophoretic and chromatographic procedures, the dinucleotides were examined for radioactivity (autoradiography). By this procedure, traces of de novo biosynthesized dinucleotides were invariably detected. In addition, however, unidentified labelled product(s) appeared during the isolation procedures. On the assumption that histamine-adenine dinucleotides are rapidly degraded in the body or in tissues, we recently studied the fate of histamine-adenine dinucleotide phosphate (structurally: histamine-ribose-pyrophosphate(ribose-2′-phosphate)adenine) after intraperitoneal injection of the labelled compound in mice and guinea pigs. This is a preliminary account of our findings in mice.