The Effects of Aging on Morphology and Collagen Composition of Rat Skeletal Muscle Arterioles

Myogenic responsiveness of rat skeletal muscle arterioles is depressed in aged Fischer rats. Impaired myogenic responsiveness of arterioles could result from alterations in cellular signaling mechanisms, vessel morphology, and/or extracellular matrix proteins. The purpose of this study was to determine whether morphological properties and/or collagen composition of skeletal muscle arterioles are altered by aging. We evaluated media cross-sectional area (CSA), wall thickness (WT), and type I and type III collagen composition in isolated first-order arterioles from the soleus and superficial gastrocnemius muscles of young (4 months) and aged (24 months) Fischer 344 rats. Arterioles were isolated, cannulated, and pressurized to 60 cm H2O via hydrostatic pressure reservoirs. Arterioles were then fixed and cut into transverse sections for measurement of CSA, WT and collagen composition (type I and III). There were no difference in media CSA with aging. Wall thickness and type III collagen content was higher (p < 0.05) in the gastrocnemius arterioles of the aged animals, and type I collagen content was lower (p < 0.05) in the soleus arterioles of the aged animals. The collagen ratio (typeI/typeIII) was also lower in the gastrocnemius arterioles from aged rats (p < 0.05). These data suggest that aging alters both vessel morphology and collagen composition of isolated first-order arterioles, and these alterations may impact myogenicity of skeletal muscle arterioles from aged rats.