Capillary supply and fibre area in locomotor muscles of horse and steer--a comparison between histochemistry and electron microscopy.

In order to investigate possible differences in variables defining capillary supply of skeletal muscle derived from two methods, the electron-microscopical and the amylase-PAS histochemical methods were applied in a study of horse and steer muscles. Samples from several locomoter muscles were taken at slaughter from one horse and one steer, divided into two and prepared separately for the two techniques. It was found that there was no difference between the two methods in the values for the capillary-to-fibre ratio. Values for mean fibre area, on the other hand, were significantly higher in the histochemically treated samples (16%, p = 0.001) and hence capillary density values lower (12%, p = 0.002). It was concluded that the two methods are comparable in their capacity to visualize capillaries, but preparation of samples for electron microscopy produces an average shrinkage of 16% of muscle fibres. As a consequence capillary density is overestimated accordingly. Discrepancies were larger for steer than horse muscles.