2.2. Animals and Experiment Design

The experiments were conducted on 60 white laboratory male Spraque–Dawley (SD) rats weighing 250 ± 5 g. Three groups of rats were created: one group contained fifteen control rats, and the other two groups contained rats subjected to experimentally induced acute abdominal organ inflammation. The second group (22 rats) experienced inflammation on the second day, while the third group (23 rats) experienced abdominal organ inflammation on the fifth day.

We chose a method for modeling inflammation in the abdominal organs by introducing fecal suspension, which is similar to an acute inflammatory process and represents the completion of the acute phase of peritonitis in terms of etiopathogenesis, clinical manifestation, and phasic flow similar to those in humans. We caused acute inflammation of the abdominal organs in the rats by introducing fecal suspension into the abdominal cavity at a rate of 0.5 mL of a 10% solution per 100 g of animal body weight [43]. No later than 20 min after the preparation stage, the resultant fecal suspension was injected into the abdominal cavity of the animals using the puncture method. Animals’ abdominal cavities were filled with fecal suspension, while the needle tip was vertically positioned, with the caudal being placed end-up to avoid injuring internal organs. The rats underwent abdominal dissections under ether anesthesia. The objects of study were the mesenteric lymph nodes, which were removed for morphological examination. The assessment of the structural and functional zones of the lymph nodes was carried out using histological, cytological, and morphometric methods.