MORPHOLOGICAL AND BIOCHEMICAL FEATURES AFFECTING THE ANTITHROMBOTIC PROPERTIES OF THE AORTA IN ADULT-RABBITS AND RABBIT PUPS

We hypothesised that there are important physiologic differences in ar terial wall structure and function with respect to antithrombotic acti vity in the very young (pre-puberty) compared to adults. Electron micr oscopy, gel electrophoresis, and activity assays were used to examine differences in aorta structure and function comparing pre-pubertal rab bits (pups) to adult rabbits. Differences in endothelial function, ext racellular matrix structure, proteoglycan (PG) distribution and glycos aminoglycan (GAG) content and function were shown. In both intima and media, total PG, chondroitin sulfate (CSI PG and heparan sulfate IHS) PG content were significantly increased in pups compared to adult rabb its. These findings corresponded to increased concentrations by mass a nalyses of CS GAG and DS GAG in aortas from pups. There was also a sig nificant increase in antithrombin activity In pups due to HS GAG. In c onclusion. 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 parr. related to increased HS GAG.