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Influences of aging and sex hormones on connective tissue metabolism in the hip joint capsule of Wistar rats were analyzed both biochemically and morphologically. As age advanced, collagen content and collagen fihril diameter of the hip joint capsule tended to increase gradually in both sexes until sexual maturation was reached. Collagen content was significantly greater in males than in females after sexual maturation. The collagen content and fibril diameter were considerably increased by ovariectomy and significantly decreased by the administration of estrogen, o r estrogen combined with progesterone, whereas they were significantly increased by the administration of testosterone in orchiectomized male rats. K e { j uiords: hip joint capsule; aging; sex hormones; colagen content; collagen fibril diameter Accepted 12.vii. 76The most prominent clinical sign of congenital dislocation of the hip in the perinatal period is relaxation of the hip joint capsule. It has been suggested by Andr6n & Borglin (1961 a, b) that female sex hormones participate in the relaxation.The aim of the present experiment is to study the influences of sex hormones on collagen metabolism in the joint capsule by analyzing the collagen content and collagen fibrif diameter. This analysis is an approach to clarifying the causative factors of the relaxation. MATERIALS AND M E T H O D S Treatment of animalsFifty-two Wistar rats, 26 females and 26 males, 3-36 weeks of age, were subjected to an analysis of the influences of aging and 180 Wistar rats, 105 females and 75 males, were subjected to an analysis of the influences of sex hormones.The rats were kept in individual cages and fed on Nihon CLEA Rat Chow and given water ad libitum. They underwent ovariectomy, orchiectomy or sham operation at 3 weeks of age with o r without subsequent hormone treatment.The hormones administered to each animal group were estradiol benzoate (20 pg, per rat), progesterone (10 mg, per rat) and testosterone propionate (2.5 rng, per rat) dissoIved in 0.1 ml of sesame oil. Control groups received sesame oil only. The injections were given twice a week subcutaneously.At 10 weeks of age, the animals were first stunned with a blow and then killed by cervical dislocation. The joint capsules of the hip and knee were dissected free of fatty tissue; the right capsules were prepared for electron microscopic examination and the left ones were hydrolyzed and assayed for hydroxyproline. ACTA ORTHOP. 47, 5 474HIROMICHI HAMA Er AL. Measurement of collagen fibril diameterAfter dissection, the specimens were fixed in 1 per cent osmium tetroxide solution in 0.2 M veronal acetate buffer, pH 7.4, dehydrated through a graded series of ethanol and embedded in Epon 812. Ultrathin sections were cut with glass-knives on an ultramicrotome (Porter-Blum MT-2). The sections were stained with uranyl acetate and examined under the electron microscope (Hitachi HS-7D type) with an accelerated voltage of 50 KV and a direct magnification of 30,000.Four areas in every section were selected at random ...

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