Calcification of the human thoracic aorta during aging.

The rate of calcification within the human thoracic aorta from completion of body growth to advanced old age was examined. Fifty-eight aortae, obtained at necropsy, were dissected into four layers: the complete intima and the separated media, which was subdivided into three tissue samples of equal thickness, defined as the media-inner, -middle, and -outer layers. The sampling sites selected for analysis were from regions of the aortic surface that were free of atherosclerotic plaques. The calcium content within each tissue layer of the aorta was determined. Arterial wall thickness and the cholesterol content of the four layers were also measured. Intimal calcification increased progressively during aging: from 1.6 micrograms Ca/mg tissue at 20 years of age to 5.2 micrograms Ca/mg tissue by 90 years of age. When intima calcium concentration was expressed by tissue volume (w/v), no significant change during aging was found. Medial calcification, as w/v and by w/w, increased throughout aging. Calcium accumulation was most marked in the middle, elastin-rich layer of the media, increasing from 1.4 micrograms Ca/mg tissue at 20 years of age to 49.50 micrograms Ca/mg tissue by 90 years of age. Calcium levels also increased in the other media layers, but at a slower rate than that found within the middle media.