Study of collagen composition and in vivo and in vitro collagen biosynthesis and maturation in 10-day-old carrageenan-induced granulomas from female guinea pigs demonstrated that old animals have decreased amounts of neutral salt and acid soluble collagen, decreased in vitro biosynthesis and turnover, and lower ratios of proline to hydroxyproline (P: OH-P) in all collagen fractions. At any age the P:OH-P ratios appeared to reflect the rate of synthesis and turnover of collagen in the tissue studied, the more soluble, more immature, less polymerized forms having higher ratios. Estradiol administration to old animals reversed the values toward those found in young animals. In both young and old, estradiol decreased total collagen content of skin and granuloma while increasing bone mass, bone collagen, and calcium content. In the granuloma, estrogen reduced the amount and content of soluble collagen, almost eliminating the acid soluble; P:OH-P ratios in all fractions were increased and proline content of the insoluble collagen, constituting 89% of the total, was significantly elevated; in vitro biosynthesis and maturation were stimulated while proline and hydroxyproline specific activities after 12–16 hr in vivo incorporation were decreased. Decreased proline and hydroxyproline specific activities after 6–30 hr of in vivo incorporation of 14C-proline were observed in aorta, skin and bone of animals treated for 6 weeks with estradiol. It is suggested that estrogens stimulate collagen synthesis, maturation and turnover by increasing the formation of a proline-rich precursor which undergoes extracellular polymerization in a modified manner at the acid-soluble stage. (Endocrinology83: 678, 1968)
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DOROTHY H. HENNEMAN (1968) studied this question.