Histotopographic Organization of Levator Ani Muscle in Laboratory Rats

Morphological organization of the levator ani muscle still remains unclear due to methodological problems in the study of the pelvic floor muscles. Therefore, the study of the histological structure of muscle tissue m. levator ani in animals is of not only theoretical but also practical importance for the study and modeling of pelvic floor dysfunction conditions in animal models. The aim is to study the enzymohistochemical and ultramicroscopic organization of the levator ani muscle in white laboratory rats. Material and methods. The study was performed on 10 laboratory Wistar rats (5 females and 5 males) aged 12–14 months. The metabolic profile of muscle fibers was determined using the Nachlass succinate dehydrogenase test. Imaging and linear measurements were carried out on a Leica UC 7 microscope (Germany), using its software. Ultrathin sections were counterstained with uranyl acetate and lead citrate, viewed nd photographed using a Hitachi HT 7700 Exalens (Japan) electron microscope. Results. All types of muscle fibers are present in levator ani muscle: slow fibers and rapid muscle fibers of typs IIA and IIB. It has been established that the total cross-sectional area of white type fibers is 3 times greater than the total area of other fibers. Significant sex differences were found in relative square parameters of glycolytic fibers in m. levator ani (p=0,009). At the ultrastructural level, it was found that in some muscle fibers the mitochondrial apparatus is well developed, in others, mitochondria are few in number, have smaller sizes, are located singly between myofibrils, without forming clusters. In such fibers, there are large accumulations of glycogen between the myofibrils. Conclusion. In the laboratory rat, the levator ani muscle is heterogeneous both in metabolic activity of muscle fibers and in ultrastructural organization. This feature of the muscle involves not only static work in creating intra-abdominal pressure and retaining the pelvic organs, but also isotonic contraction, acting as a synergist to ensure the movement of the tail.

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