Capillarity of elite cross‐country skiers: a lectin (<i>Ulex europaeus</i> I) marker

Abstract

Capillary morphometrics in human skeletal muscle has been limited by technical problems in visualization. The purpose of this study was to develop a method for identifying capillary endothelium at the light level of resolution and to reassess the skeletal muscle capillarity in trained and untrained subjects. A lectin system of biotinylated Ulex europaeus I (UEA‐I), a vascular endothelial marker, provided a stain dense enough for direct computer‐aided image analysis. A morphometric comparison was made between Andersen's periodic acid‐Schiff and the UEA‐I capillary stains on tissue sections of human skeletal muscle. When identical fibers from adjacent sections were compared, the capillary density was 6% and cap fiber was 9% greater using the lectin method. Biopsies from 17 cross‐country skiers were compared with those of 8 age‐matched sedentary controls. The capillary density in the triceps muscle for the skiers was 536.1 ± 33.1 compared with 296 ± 17.7 for the controls. Longitudinal profiles that appear in skeletal muscle cross‐sections suggest a more isotropic (random orientation) configuration of the capillary bed than proposed by the Krogh model. There were 50.6% more longitudinal profiles in the trained samples. The UEA‐I lectin appears to be a valid and potentially useful marker for computerized image analysis of non‐pathological vascular endothelium, and the differences in capillarity between trained and untrained individuals may be greater than previously reported.