Summary
We hypothesised that there are important physiologic differences in arterial wall
structure and function with respect to antithrombotic activity in the very young (pre-puberty)
compared to adults. Electron microscopy, gel electrophoresis, and activity assays
were used to examine differences in aorta structure and function comparing prepubertal
rabbits (pups) to adult rabbits. Differences in endothelial function, extracellular
matrix structure, proteoglycan (PG) distribution and glycosaminoglycan (GAG) content
and function were shown. In both intima and media, total PG, chondroitin sulfate (CS)
PG and heparan sulfate (HS) PG content were significantly increased in pups compared
to adult rabbits. These findings corresponded to increased concentrations by mass
analyses of CS GAG and DS GAG in aortas from pups. There was also a significant increase
in antithrombin activity in pups due to HS GAG. In conclusion, differences in both
structure and antithrombin activity of aortas from pups compared to adult rabbits
suggest that young arteries may have greater antithrombotic potential that is, at
least in part, related to increased HS GAG.