CAPILLARY NETWORK IN SLOW AND FAST MUSCLES AND IN OXIDATIVE AND GLYCOLYTIC MUSCLE FIBRES

Abstract

The aim of this study was to compare capillary network in slow and fast muscles and also in oxidative and glycolytic muscle fibres. Soleus (SOL) and extensor digitorum longus (EDL) muscles were excised from five female rats. Capillaries and muscle fibres were demonstrated on thick tissue sections by a triple immunofluorescent method. Stacks of perfectly registered optical images were captured by a confocal microscope and further analysed. Applying stereological methods (POINTGRID, FAKIR and SLICER plugin- modules of the Ellipse programme), we estimated the mean length of capillaries, adjacent to individual muscle fibre, per unit fibre length (Lcap/Lfib), per unit surface area of the fibre (Lcap/Sfib) and per unit fibre volume (Lcap/Vfib) in the slow SOL and in predominantly fast EDL muscle, and separately in oxidative and glycolytic fibres of EDL muscle. The length of capillaries per unit fibre length was larger in SOL than in EDL muscle, however, capillary length per unit fibre volume was larger in EDL muscle. There was no difference in the length of capillaries per unit fibre surface area between the two muscles. Oxidative and glycolytic fibres differ in the length of capillaries per unit fibre surface area (Lcap/Sfib). This parameter probably reflects the oxidative capacity of muscle fibres. In conclusion, capillary supply is evidently well adapted to different muscle fibre types; consequently, an average capillary supply of a heterogeneous muscle depends on the muscle composition. The estimated mean values blur some intrinsic differences.