Static mechanical properties and chemical composition of the aorta of spontaneously hypertensive rats: a comparison with the effects of induced hypertension.

The static elastic properties and medial scleroprotein content of the aorta have been examined in spontaneously hypertensive rats (AS strain) aged 6 and 20 weeks (group SH). The results are compared with data from two previous studies on normal (group N) and induced hypertensive animals (group H). Spontaneous hypertension is associated with a relative increase in elastin and decrease in collagen when compared with the normal aorta. These changes are similar to, although smaller in magnitude than, those associated with induced hypertension. Elasticity measurements show that the functional stiffness (incremental strain) of the aorta in group SH is greater than normal. However, this difference diminishes with age, suggesting an adaptive response which tends to maintain the functional stiffness near to normal levels.