HYPERTROPHY OF LEVATOR ANI MUSCLE OF RAT INDUCED BY TESTOSTERONE - AN ELECTRON MICROSCOPE STUDY

The recovery process of levator ani muscle of rat atrophic by castration has been studied by electron microscope after testosterone treatment. Muscles have been observed 1-5, 7, 15, and 30 days after the beginning of treatment. The testosterone treatment produces in the atrophic muscle a rapid increase of the weight that returns to the normal values after a month. The diameter of the fibers increases above the normal values between day 5 and 7. Besides, the myofibrils diameter shows a progressive increase and the maximum values are reached between day 5 and 15. The electron microscopy shows that already after 24 hours of treatment several changes are detected in the fibers. The glycogen amount increases until day 5 so that large masses of granules are found whether at the fiber periphery or in the interfibrillar spaces. After day 5 of treatment, the glycogen amount slowly decreases. The ribosomes and polysomes are very abundant especially in the first periods of treatment. The nucleoli show a concomitant increase. Clusters of mitochondira appear at the periphery of the fibers and are still numerous after 15 and 30 days of treatment. The disorganized areas which have been found in the atrophy gradually disappear. They are scarce after 15 days and absent after a month. At this stage they appear to be substituted by contractile material. In fact, the fibers undergo an almost complete restoration of the atrophy lesions so that the recovery process of levator ani muscle by the hormonal influence can be considered accomplished after a month. © 1969.