Age-related changes in type III collagen and tenascin in the rat submandibular gland

Abstract

We investigated biochemically and immunohistochemically the age-related changes in type III collgen and tenascin in the rat submandibular gland. Tha DNA content tended to decrease beginning at 14 weeks after birth. The total protein content decreased with age while the hydroxyproline content gradually increased. The amount of type III collagen, which is distributed in interlobular connective tissue, gradually decreased after 14 weeks, as did the ratio of type III to type I collagen. Tenascin, which is distributed in the basement membrane of ducts and vessel walls, decreased markedly between 14 to 21 weeks after birth. These findings suggest that collagen and tenascin remain in the tissues after completion of functional differentiation, although their quality and quantity change with age. They are both instrumental in the construction of infant submandibular glands during the first 14 weeks of life.