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Abstract
Physiological changes with advancing age and the influence of sex hormones on elastin in the hip joint capsule of rats were studied both biochemically and morphologically. Elastin content of the joint capsule was greater in females than in males at 10 weeks of age. Staining of ultrathin sections with Verhoeff iron hematoxylin followed by lead citrate (VIH-LC) demonstrated that the elastic fibers of specimens from infant rats were characterized by a small elastin core formed by aggregation of elastin fibrils in the center of closely packed microfibrils. With advancing age the diameter of the elastic fiber of the hip joint capsule tended to increase gradually in both sexes until sexual maturation was reached. In specimens from adult rats, the elastic fiber consisted of an increased solid elastin core surrounded by loosely packed microfibrils. The diameter of the elastic fiber and the ratio of the central elastin to the peripheral microfibrils were greater in females than in males after sexual maturation. The elastin content, the fiber diameter and the ratio of the central elastin to the peripheral microfibrils were considerably increased by administration of estrogen and decreased by ovariectomy or the administration of testosterone in ovariectomized female rats. It is suggested that the imbalance of estrogen metabolism may be a major contributing factor to the mechanical properties of the hip joint capsule in growing rats.