Collagen elastin content, tissues

Table3.2 Collagen and elastin content of some tissues (g/100 g of dry weight)...

The elastic fibrous component of connective tissue, elastin, has often been examined by use of wide-angle diffraction techniques, applied to ligaments as sources of high elastin content. Earliest studies showed collagen-type diffraction (104), and Kolpak (126) found that stretching... 

Since the presence of hydroxyprohne is unique in collagen elastin contains a small amount), the determination of collagen content in a coUagen-rich tissue is readily done by assaying the hydroxyproline content. 

Blood and lymphatic vessels are soft tissues with densities which exhibit nonlinear stress-strain relationships [1]. The walls of blood and lymphatic vessels show not only elastic [2, 3] or pseudoelastic [4] behavior, but also possess distinctive inelastic character [5, 6] as well, including viscosity, creep, stress relaxation and pressure-diameter hysteresis. The mechanical properties of these vessels depend largely on the constituents of their walls, especially the collagen, elastin, and vascular smooth muscle content. In general, the walls of blood and lymphatic vessels are anisotropic. Moreover, their properties are affected by age and disease state. This section presents the data concerning the characteristic dimensions of arterial tree and venous system the constituents and mechanical properties of the vessel walls. Water permeability or hydraulic conductivity of blood vessel walls have been also included, because this transport property of blood vessel wall is believed to be important both in nourishing the vessel walls and in affecting development of atherosclerosis [7-9]. 

The composition of normal human arterial tissues is altered with age in many aspects. Table B6.7 lists the observed changes in human aorta, pulmonary and femoral arteries [20]. There is a tendency that both the dry matter and nitrogen content of arterial tissues decreases with age. However, the relative quantity of collagen [22] and elastin [23, 24] in the arterial wall remains almost unchanged with age. Below the age of 39, the wall of human thoracic aorta has 32.1 5.5% elastin, between the age 40-69, the wall contains 34.4 9.3%, and from 70-89, the elastin content is 36.5 10.1 [24]. 

The collagen content of the thoracic aorta was expressed in mg/100 mg of dry, lipid-free aortic tissue. This was done by using the factor of 7.46 to convert the values of hydroxyproline into those of collagen. Elastin is expressed as mg of hydroxyproline liberated by hydroxylysis of this protein by 100 mg of dry, lipid-free aorta. The amount of nitrogen in the collagen extract was determined by the procedure of Houck and Jacob (1958). Histological sections of the aorta and coronary arteries were made and strained by the Oil-Red-0 method (1968). 

The ECM that surrounds cells also contains variable levels of HA. It is composed predominantly of structural proteins such as collagen and elastin, as well as proteoglycans, and a number of glycoproteins. The HA content is greatest in embryonic ECM, and in tissues undergoing rapid turnover and repair. The basal lamina or basement membrane that separates dermis and epidermis is also considered an ECM structure. The basal lamina contains HA, though the precise structural position is not known. Loss of basement membrane HA in the skin of diabetic patients correlates with skin stiffness.50... 

Diseases of elastic tissue are few compared with those that affect collagen, and in these destruction of preformed elastic fibers appears to occur only in localized areas, particularly in the walls of blood vessels and in the skin. In arteriosclerosis loss of elasticity and breakdown in the structure of the elastic elements in the media of arteries is accompanied by calcification of the media and the development of calcified plaques in the intima. Since calcification of the media may be seen to occur without the development of atheromata, it is thought that this change may be associated in the first place with age. Other age-related changes looked for have been changes in the gross content of elastin in the media and changes in the amino acid... 

---