A stereological analysis of the effect of 19-nortestosterone (Durabolin) on rat skeletal muscle.

It is known that some anabolic steroids are capable of increasing the sizes of skeletal muscles or increasing their mechanical performance. The present study was undertaken to establish quantitatively the alterations which occur in skeletal muscle fibres as a result of the injection of 19-nortestosterone (nandrolone phenyl proprionate). Specimens of diaphragm were obtained from the experimental and control animals and prepared for electron microscopy and stereological analyses. Following low doses of the steroid stereological analyses have shown that in Type I and in intermediate fibres their mitochondrial volume proportions increase though their myofilament contents decrease. With higher doses, stereological analyses have shown that the mitochondrial volume proportions were increased particularly in intermediate fibres whilst the myofilament content of Type I and II fibres was significantly reduced.