Introduction: Irisin is a newly discovered adipo-myokine, that has a significant influence on body metabolism. Available data about this peptide is still insufficient. The aim of the study is to provide some initial information about body distribution of irisin in rats.
Methods: The studied group consisted of 27 10-week-old female Wistar rats, which received intraperitoneally ~0.7 mcCi of iodine-125 labeled irisin. The studied rats were divided on five subgroups: six were decapitated after 15 min, five after 30 min, 1 h and 2.5 h and last six after 5 h. The samples from blood, kidneys, liver, subcutaneous and visceral fat, heart, skeletal muscles, diaphragm, adrenals, brain and cerebellum were taken, scaled and the radiation was measured (counts per minute (CPM)). The same procedure was applied for five rats which received only saline intraperitoneally control group.
Results: The maximum radiation (CPM/1 g) in the blood was registered 1 h after the injection. At that moment the highest radiation was detected in kidneys. After 1 h the maximum radiation was registered also in liver, heart, and skeletal muscles. In case of brain and cerebellum the maximum point was depicted after 2.5 h. The diaphragm, subcutenaus fat, visceral fat, and adrenals presented very high radiation just after the injection, which decreased rapidly with time. At every point of the study the studied group tissue radiation was significantly higher than in the control group (P<0.05).
Conclusions: It may be assumed that intraperitoneally injected irisin has a standard distribution associated with blood perfusion and crosses the bloodbrain barrier. There is no specific accumulation in described organs. The initial high radiation of diaphragm, subcutaneous fat, visceral fat and adrenals may be associated with the place of injection, thus is not reliable.