Relationship between Aortic Histamine Formation and Aortic Albumin Permeability in Atherogenesis 1

Abstract The relationship between aortic histamine-forming capacity (HFC) and albumin permeability was examined in intima—media preparations of ascending aorta and aortic arch segments of male, Dutch-belted rabbits maintained on Purina Rabbit Chow containing 0.5% cholesterol for 2- and 4-week periods; pair-fed controls were maintained on Purina Rabbit Chow. Aortas from rabbits maintained on the 2-week cholesterol regimen showed no evidence of atherosclerosis, while those from rabbits on the 4-week regimen had substantial subendothelial lipid, as determined by oil red O staining of fresh-frozen sections. Aortic albumin permeability, measured in terms of aortic content of bovine serum albumin conjugated to fluorescein isothiocyanate (FITCBSA) under steady-state conditions, was highest in the 2-week treatment group (43.8 ± 6.3 ng/mm2, P < 0.05) than in either control segment (34.4 ± 1.86 ng/mm2) or similar segments from the 4-week treatment group (31.4 ± 3.38 ng/mm2). Similarly, the ascending aorta and aortic arch segments of this same 2-week treatment group had a significantly higher (P < 0.05) HFC (16.82 ± 0.8 dpm/mm2) than corresponding control (15.13 ± 0.87) and 4-week (13.85 ± 0.99 dpm/mm2) treatment groups. Linear regression analyses of the intraaortic FITCBSA content against the aortic HFC yielded a significant correlation coefficient (r = 0.59, P < 0.05) between these parameters in the 2-week treatment group only. These results indicate that the rate of aortic histamine synthesis is increased during early stages of the atherogenic process, and that a causal relationship may exist between the rate of this histamine synthesis and the increased aortic transmural albumin permeability which occurs under these preatherosclerotic conditions.