title: Vascularity of myocardium and gastrocnemius muscle in rats selectively bred for endurance running capacity.
abstract: We tested the hypothesis that changes in the arteriolar branching architecture contributed to increased running capacity of rats subjected to two-way artificial selection for intrinsic aerobic endurance treadmill running capacity resulting in strains of low-capacity and high-capacity endurance rats. Hearts and gastrocnemius muscles were harvested from each strain, and the microvasculature's branching geometry measured from micro-CT images. The vascular branching geometry of the hearts and skeletal muscle from the high capacity was indistinguishable from low-capacity rats. Our hypothesis was not supported. Neither remodeling nor an increase in arteriolar microvasculature branching appears to play a role in the enhanced performance of the high capacity rats. We are led to speculate that endothelial tolerance for shear stress and/or increased coupling of myocardial muscle fiber metabolic-to-contractile function is increased in the high-capacity runner strain to the effect of allowing either higher flow rate per unit volume of muscle or more efficient use of oxygen and nutrients in the high-capacity endurance rats.
authors.affiliation: Department of Physiology and Biomedical Engineering, Mayo Clinic, College of Medicine, Rochester, Minnesota 55905, USA.
authors.forename: Patricia E
authors.initials: PE
authors.lastname: Beighley
authors.forename: Mair
authors.initials: M
authors.lastname: Zamir
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Wentz
authors.forename: Lauren G
authors.initials: LG
authors.lastname: Koch
authors.forename: Steven L
authors.initials: SL
authors.lastname: Britton
authors.forename: Erik L
authors.initials: EL
authors.lastname: Ritman
mesh_terms: D000818:Animals; D005260:Female; D006321:Heart / Q000502:physiology*; D021621:Imaging, Three-Dimensional / Q000379:methods; D018482:Muscle, Skeletal / Q000502:physiology*; D010807:Physical Endurance / Q000502:physiology*; D051381:Rats; D012420:Running / Q000502:physiology*