Heat-Induced Changes in the Mechanics of a Collagenous Tissue: Isothermal Free Shrinkage

The curves obtained for skin samples of different ages and species by hydrothermal isometric tension ("HIT") measurement are compared to those obtained by differential scanning calorimetry (DSC) under the same thermal conditions (for a rise in temperature at a rate of 1.0 degrees C/min). Collagen denaturation, observed by DSC, directly affects the kinetics of the tension variations in the first part of the "HIT" curves, including the early peak due to the presence and destruction of the heat-labile cross-links in the collagen network. The presence of cross-links is in term shown to delay collagen denaturation to an extent which depends in part on their heat-stability. The final part of the "HIT" curves reflecting the effects of heat in the stable polymeric collagen network is no longer affected by collagen denaturation. Thus, both "HIT" and DSC are useful methods to evaluate collagen reticulation in connective tissues.