The effect of experimental renal hypertension on the response of the rabbit aorta to vitamin D.

Vitamin D was administered to groups of normal rabbits and rabbits made hypertensive by clipping the renal artery and removing the opposite kidney. The effect of vitamin D administration alone (II), renal hypertension alone (III), and both combined (IV) on the degree of aortic mineralization, aortic diameter and aortic connective tissue composition was investigated. The mineral content of the aorta increased from a mean of 2·00% in control rabbit aortas (I) to 5·79% in Group II, 5·29% in Group III and 19·71% in Group IV. A significant synergism between the two treatments was demonstrated. Increased aortic ash concentration was shown to be associated with an increase in the internal diameter of the aorta according to the regression equation: diameter (mm)=0.108+3·99, where =aortic ash content in mg%. Neither hypertension nor vitamin D alone had an effect on the connective tissue composition of the aorta, but when combined they were associated with an absolute increase in the amounts of collagen, elastin and non-collagenous alkali-extractable proteins.