Elastin and collagen accumulation in rabbit ascending aorta and pulmonary trunk during postnatal growth. Correlation of cellular synthetic response with medial tension.

Absolute and relative quantities of elastin, collagen, and DNA in anatomically defined segments of rabbit ascending aorta (AA) and pulmonary trunk (PT) were compared at intervals from birth to 2 months of age. Identical in size, weight, and composition at birth, the vessels maintained similar lengths and diameters at each age but diverged markedly in weight and scleroprotein content after 1 week. By 2 months, 3 times as much elastin and 1.7 times as much collagen had accumulated in the AA as compared to the PT. By contrast, the increase in total DNA content was the same for both segments. Differences in total fibrous protein accumulation, total elastin accumulation, and elastin content relative to DNA paralleled differences in estimated total medial tangential tension. Proportions of elastin and collagen relative to dry weight increased markedly only between 4 and 2 weeks of age and not thereafter despite continuing rapid growth, steadily increasing medial tension, and increasing total scleroprotein content. Thus, medial cells were capable of adapting their quantitative scleroprotein synthetic response to differences in medial tension throughout growth but established a fixed qualitative response within 2 weeks.