EFFECT OF AGING AND DIETARY RESTRICTION ON MATRIX GLA PROTEIN AND OTHER COMPONENTS OF RAT TRACHEAL CARTILAGE

Age-related changes in connective tissues can alter their functions of elasticity, compressibility and support. Matrix Gla protein (MGP) is a vitamin K-dependent connective tissue component of unknown function. We have purified bovine MGP, and developed a specific radioimmunoassa y for it. Since it is found in highest concentration in cartilage, we have developed quantitative extraction methods for MGP, and examined t he age-related changes of MGP relative to other components found in th e cartilage matrix. The ratio of hydroxyproline to MGP increases with age, while the ratio of glycosaminoglycan to MGP is constant. No effec t is seen for MGP in the dietary restricted rat with prolonged lifespa n, while both hydroxyproline and glycosaminoglycan contents of trachea l cartilage are significantly increased by dietary restriction (p less -than-or-equal-to .05). These data show that MGP and glycosaminoglycan concentration are relatively constant in rats from 6 to 30 months of age, while hydroxyproline concentration increases with age.