MECHANICAL CHANGES IN RAT TAIL TENDONS INDUCED BY DIBASIC AMINO-ACIDSAS A FUNCTION OF AGE

Rat tail tendons from 54-day-old and 900-day-old animals were incubate d with different concentrations of the dibasic amino acids, lysine and arginine. We observed a significant incorporation of these amino acid s into the tendons. Uniaxial tension tests and relaxation experiments were performed at strain levels within the linear portion of the stres s-strain relationship. The incorporation of the amino acids resulted i n a decrease of ultimate stress and maximum Young's modulus and, after separation of the elastic and viscous stress components, in a decreas e of the elastic fraction. The incorporation of amino acids and the re sulting mechanical alterations were more pronounced in the young anima ls. The reversibility of the effects induced by the amino acids was te sted. After the glycosaminoglycan chains were digested with chondroiti nase ABC, we showed that the dibasic amino acids bind predominantly to the proteoglycan matrix. A possible analogy to the effects of amino a cid incorporation on biomechanics and swelling with a monovalent catio n such as Na+ is discussed.