Impaired collateral development in mature rats

The effect of maturation on collateral development of resistance arteries was investigated. Three to four sequential mesenteric arteries were ligated to create collateral pathways in anesthetized young (approximately 200 g) and mature (approximately 600 g) rats. Blood flow was similarly elevated in collaterals of young and mature animals. In vivo inner arterial diameter was increased only within young collaterals (33 +/- 7%, P < 0.001). Increases in number of intimal nuclei (57 +/- 10% vs. 52 +/- 14%) and cross-sectional medial area (33 +/- 13% vs. 38 +/- 5%) were similar between young and mature collaterals. Relative to the same animal controls, collateral endothelial nitric oxide synthase mRNA was increased as much in mature as in young rats. Proteomic analysis revealed significant differences in protein expression with maturation between control arteries as well as flow-loaded collateral vessels. The results indicate that, whereas intimal and medial remodeling events were similar in collaterals of young and mature rats, luminal expansion occurred only in young rats. Alteration in arterial protein expression with maturation and altered responses to stimuli for collateral development may contribute to this impairment.