Local aortic histamine metabolism and albumin accumulation. Differences between blue and white areas

Relationships between histamine metabolism, histamine content, and albumin accumulation were examined in Evans blue dye stained areas (blue) and unstained (white) areas of normal canine aortas. Results indicated that, while no differences existed in histamine methyltransferase-mediated catabolism, both histidine decarboxylase-mediated histamine synthesis and the histamine content of blue regions were significantly greater (p less than 0.005) than in contiguous white areas. Blue areas also showed significantly higher fluorescein-labeled albumin accumulation than white areas. By multiple regression analysis, a significant relationship (r = 0.81) was obtained between local aortic albumin accumulation and combined influences of local histidine decarboxylase activity and histamine content. The best predictor in this case was the local histidine decarboxylase activity. These data indicate that blue areas, believed to represent areas of spontaneous hemodynamic-induced vascular injury, have a larger nascent histamine pool than do contiguous white areas and that the distribution of histamine and histamine synthesis in the aorta is highly variable depending on the region examined. The data also suggest that local aortic histamine synthesis in blue areas may play a significantly role in mediation of the increased albumin accumulation observed in these regions.