Age-dependent variations of diastolic stiffness and collagen content in rat ventricular myocardium.

A parallel investigation on collagen content and diastolic mechanical properties has been performed on myocardial specimens isolated from male albino Wistar rats of different age groups (1-5 days, 10-20 days, 2 months, 8 months, 18 months, 24-26 months). Total water content, inulin-distribution space, protein concentration were determined together with hydroxyprolin content of the tissue. Mechanical properties of isolated papillary muscles were characterized in terms of static, dynamic, and plastic response to strain. During maturation (from birth to 2 months) the increase of collagen content is paralleled by an increase of static elasticity and by a reduction of plasticity. During maturity (2-8 months) and ageing (8-26 months) the collagen concentration in myocardial tissue still increases, but this change is associated to a reduction of the static components and to an increase of dynamic components of myocardial stiffness. A comparison between specimens from right and left ventricular myocardium indicates that a higher collagen content in the right ventricle is associated with a higher static elasticity.