[Structural approach of vascular aging]

The cardiovascular system is one of those target-organ systems of senescence where the effects of physiological ageing meet the consequences, accumulated with time, of pathological disorders. In man, these two processes are not easily disentangled, and despite the advances achieved in ultrasonic techniques the approach of structural parameters remains difficult. On the other hand, the morphological and functional unicity of the vascular wall in different species is such that observations made in animals are relevant. In rats, the structure-function relationship can be determined by histomorphometric analysis of the myocardium and vascular wall under standardized conditions of treatment. As the animals get older, the cardiac mass, related or not to body-weight, increases while the cardiac efficacy decreases. Hypertrophy of the heart is accompanied by a change in the enzymatic property of myosin. Simultaneously, the walls of the greater arteries become thicker, more rigid and less compliant, hypertrophy of the smooth muscle cells being an essential component of vascular wall thickening. At the same time, the collagen fraction and the amount of collagen-bound calcium increase. The elastic component decreases, at least relatively, and the elastin-collagen ratio clearly diminishes with age. Altogether, these alterations are not different from those observed in human arterial hypertension. They result in a lesser permeability of the tunica media, facilitate the accumulation in the subendothelium of lipidic and/or proteinic compounds originating in plasma and constitute a link between ageing and atheromatous processes.