The effect of intra-abdominal pressure experimental changes on the ultrastructure of the rat’s levator ani muscle

In clinical practice, it is well known that an increase in intra-abdominal pressure can lead to disorders in the functioning of internal organs, cause the development of multiple organ failure and the formation of pelvic organ prolapse. Despite the fact that the pelvic bottom along with the muscles of the anterior abdominal wall and the diaphragm, takes an active part in the formation of intra-abdominal pressure, so far there are practically no morphological studies of the muscles of the pelvic diaphragm and their reactive changes that occur in response to an increase in intra-abdominal pressure. The aim of the study was to study the ultrastructural rearrangements of the levator ani muscle in response to experimentally formed states of increase and decrease in intra-abdominal pressure. The work was performed on 21 male outbred adult white laboratory rats. It has been established that after damage to the myofibrillar apparatus of the muscle fibers of the levator ani muscle in response to an increase in intra-abdominal pressure, the processes of sarcoplasmic adaptation and activation of the synthetic apparatus begin in them, which leads to a gradual restoration of their structure to its initial state. These changes are subject to certain time dynamics. 4 weeks after the increase in intra-abdominal pressure, a slight atrophy of the myofibrillar apparatus is observed and expansions of the intermyofibrillar cytoplasmic matrix appear. In mitochondria distinctly expressed irreversible changes in mitochondria occur, many mitochondria die. Subsequently, a significant amount of glycogen granules appears between the myofibrils, the structure of the myons is restored. Eight weeks after the start of the experiment, the structure of most muscle fibers is restored almost completely. The structure of the levator ani muscle did not change during the simulation of reduced intra-abdominal pressure in comparison with the control group at all periods of observation. In general, the study shows that the levator ani muscle skeletal muscle tissue has a high mechanic-dependent plasticity, which manifests itself in compensatory rearrangements of the ultrastructure of its fibers in response to changes in intra-abdominal pressure.