Effect of age on the vasodilatory action of elastin peptides

We have recently shown, on young adult rat aorta rings, that elastin peptides induce a dose and endothelium-dependent vasodilation mediated by the 67 kDa subunit of the high affinity elastin-laminin receptor and, at least in part, by EDRF (NO). Here we have studied the effects of elastin peptides at circulating concentrations and below, on noradrenaline-contracted rat aortic rings, as a function of age. First, we have observed that, unlike 2-month-old (2M), 4-6-month-old (4M) and 12-month-old (12M) rat aorta rings, 30-month-old (30M) rat aorta rings were unable to maintain their contraction in long lasting experiments. Secondly, elastin peptides at physiological circulating concentrations (10(-6)-10(-3) mg/ml) induce a dose-dependent vasodilation on 4M rings. By contrast, only higher elastin peptide concentrations (10(-3) mg/ml) were effective on 12M rings, whereas rings from both younger (2M) and older animals (30M) did not respond to elastin peptides. Finally, using lactose and laminin as inhibitors, we have demonstrated that elastin peptide-induced vasodilation on 4M and 12M rings is mediated by the 67 kDa subunit of the elastin-laminin receptor. These experiments suggest that the functional availability of the 67 kDa subunit of the elastin-laminin receptor changes with age. It could be hypothesized that in young animals (0-2M) the reusable shuttle role recently demonstrated for the 67 kDa receptor subunit during elastic fiber formation leads to a major decrease in its availability for signal transduction. On the contrary, in adult animals. (4-12M), when developmental elastogenesis is completed, this subunit is essential for extracellular signal transduction. Inefficiency of this receptor in old animals (30M) can be attributed to its uncoupling from its transduction pathway, as previously shown on human cells. Finally, the age-dependent variations of circulating elastin peptide concentration and elastin-laminin receptor responsiveness to elastin peptides are two independent parameters which could influence the vascular tension regulation.