Capillary density of tenotomized skeletal muscles. I. Experimental study in the rat.

Our purpose was to study the capillary density of rat gastrocnemius muscle by microangiography 7-21 days after achillotenotomy or immobilization in a plaster cast. Sixteen animals were tenotomized, 12 immobilized in a plaster cast, and 4 served as controls. The number of capillaries was counted per 1,000 muscle fibres from each sample. No site differences were found in control muscles, where on an average 1,250 capillaries per 1,000 muscle fibers were found. After tenotomy the number of capillaries was decreased 35%, 31%, and 32% on days 7, 14, and 21, respectively. In immobilized muscles the decrease in capillary density occurred slowly, the corresponding decrease being 23%, 33%, and 28% on days 7, 14, and 21, respectively. These results indicate that the capillary density of muscular tissue is greatly decreased following the disuse produced by tenotomy or immobilization.