A comparative study of aging of the elastic fiber system of the diaphragm and the rectus abdominis muscles in rats

In the present study the age-related changes of the striated muscle elastic fiber system were investigated in the diaphragm and rectus abdominis muscl es of 1-, 4-, 8 - and 18-month-old rats. The activation patterns of these m uscles differ in that the diaphragm is regularly mobilized tens of rimes ev ery minute during the entire life of the animal whereas the rectus abdomini s, although mobilized in respiration, is much less and more irregularly act ivated. The elastic fibers were stained by the Verhoeff technique for matur e elastic fibers. Weigert stain was used to stain mature and elaunin elasti c fibers, and Weigert-oxone to stain mature, elaunin and oxytalan elastic f ibers. The density of mature and elaunin elastic fibers showed a progressiv e increase with age, whereas the amount of oxytalan elastic fibers decrease d in both diaphragm and rectus abdominis muscles and their muscular fascias , These age-related quantitative and structural changes of the elastic fibe r system may reduce the viscoelastic properties of the diaphragm and rectus abdominis muscles, which may compromise the transmission of tensile muscle strength to the tendons and may affect maximum total strength.