Species differences of elastic and collagenous tissue--influence of maturation and age

Age-dependence of mechanical and biochemical parameters has been studied in pigeons between 1 and 80 months and in rats between 1 and 30 months. In pigeons, body weight, bone weight and breaking strength of femur and tibia are only slightly increased during this time indicating that in this species maturation takes place as early as during the first 4 weeks after hatching. In contrast, in rats a sharp increase of these parameters during maturation and a significant decrease during senescence was observed. Similarly, ultimate load of aorta rings was only sightly influenced by aging in pigeons, but showed in rats a biphasic pattern due to maturation and aging. The prepatagial tendon in pigeons gives the unique opportunity to study an organ consisting mostly of elastic fibres. Only a slightly increase of strength during the whole life-span, but no decrease during senescence was found. Tail tendons in rats consisting almost entirely of collagen fibres show a pronounced increase during maturation and a decrease during aging. The mechanical values were followed closely by the collagen content, but not at all by the elastin content.