Abstract
The aim of the present study was to investigate the effect of age on the property of collagen, the solubility and platelet aggregation activity, prepared from human aorta.
The tunica media prepared from 8 females aged 13 to 91 years was repeatedly extracted with 0.5M NaCl containing 0.02M EDTA pH 7.4, 0.5M acetic acid, 5M guanidine in 0.1M Tris-HCl pH 7.4 and hot 0.1M NaOH (98°C, 45min.) in this order.
To estimate collagen content of each fraction both hydroxyproline and hydroxylysine were determined, since hydroxylysine was an amino acid specific for collagen. Percent distribution of both amino acids among fractions was in good agreement with each other.
The proportion of neutral salt-, acetic acid-and guanidine soluble collagen to the total collgaen decreased with advancing age, whereas insoluble collagen increased.
Elastin was prepared from hot 0.1M NaOH residue by dithiothreitol reduction and was subjected to amino acid analysis. No significant differences were found among young and old individuals.
The insoluble collagen fraction was prepared from 5M guanidine residue by treating with 0.5% deoxycholic acid followed by homogenization in cold saline. The relative platelet aggregation activity of this fraction gradually decreased with age, suggesting that the insoluble collagen had undergone a further structural change.
These observations indicate that (1) the stepwise extraction enables to correctly estimate the agerelated decline in solubility of collagen and (2) the insoluble collagen would become less potent with age in a biological activity to induce platelet aggregation.
