Proteoglycan distribution in areas of differing permeability to Evans blue dye in the aortas of young pigs. An ultrastructural study.

We studied proteoglycan distribution in areas of spontaneously occurring high and low permeability by TEM examination of ruthenium red-stained sections of the aortic arch of normolipemic and hyperlipemic pigs. We noted granules of two sizes: those smaller than 20 nm contained heparan sulphate, and those from 20 to 50 nm in size contained chondroitin or dermatan sulphate. In the aortas of pigs fed a normal diet, there were significantly more granules of both types in low permeability areas than in areas permeable to Evans blue dye. This is consistent with the theory that glycosaminoglycan provides a component for the control of aortic permeability. In the aortas of pigs fed cholesterol, there was an accumulation of lipid-filled monocytes in areas of high permeability and an increase in proteoglycan granule concentration, suggesting an increase in glycosaminoglycan concentration, which may be the precursor to extracellular lipid deposition.