As one of the possible causes of circulatory disturbance, wrapping of the torsos of rats has been reported to produce liver injuries, including centrilobular coagulative necrosis4, inflammatory cell infiltration, fibrosis and granulomatous inflammation5. should be differentiated from those caused by evident exogenous pathogens such as chemicals or microorganisms. Keywords:rats, liver, granulomatous inflammation, calcium deposit, hypoxia == Introduction == In laboratory animals, including mice, rats, dogs and primates, focal aggregates of inflammatory cells such as microgranulomas are common spontaneous lesions in the liver, irrespective of age1. However, the cause of this focal inflammatory change remains to be clarified, although the participation of agents from the intestinal tract via the portal blood flow, such as bacteria and endotoxins, is suspected. With aging, spontaneous occurring microgranulomas in rat livers increase in size, show a diffuse distribution and finally appear as granulomatous inflammation in severe cases. On the other hand, larger-sized focal granulomatous lesions as in the present cases are rare, and their possible cause is difficult to clarify. Chemicals, including carbon tetrachloride, are known to induce granulomas in the livers of laboratory animals1,2. Since it is difficult to distinguish morphologically between spontaneous and induced granulomatous lesions, it is important to clarify the possible cause of spontaneous lesions. In regard to hepatocellular necrosis caused by circulatory disturbance, the occurrence of infarct in the liver is usually rare because the liver has two sources of blood supply, the hepatic artery and portal vein3. As one of the possible causes of circulatory disturbance, wrapping of the torsos of rats has been reported to produce liver injuries, including centrilobular coagulative necrosis4, inflammatory cell infiltration, fibrosis and granulomatous inflammation5. Similar lesions are known to occur in women wearing severely restrictive corsets, and this is referred to as corset liver6. Experimental investigations on the effects of wrapping the torso with a bandage covering the entire body have been carried out using rats4, guinea pigs7and dogs8. In general, wrapping or bandaging seems to cause congestion in the livers of humans6and animals4,7,8and ischemia following the congestion induces hepatocellular necrosis and the accompanying changes. The focal granulomatous inflammation in the liver of the rats in the present cases was characterized by histological findings such as the presence of foreign body (S)-3,5-DHPG multinucleated giant cells engulfing calcium deposits. This lesion (S)-3,5-DHPG was found in 5 animals, and all of their regional development sites were at the tip of a fissure (1 case with a fissure in a (S)-3,5-DHPG sub-lobation and 4 cases with an interlobar fissure in the medial lobe) in the liver. Considering the site-specific occurrence, circulatory disturbance due to physical external pressure or extension force is suspected to play a possible important role in the pathogenesis of these lesions, because these sites are easy to move by external pressure Rabbit Polyclonal to GPR174 or extension force. The site of the medial lobe is known to develop tension lipidosis frequently as a result of tension from theligamenta falciforme hepatis. To obtain clues about the pathogenesis of this focal granulomatous inflammation in the liver, we examined various materials histologically as follows: 1) rat livers with sub-lobation in the left lobe (to examine the presence or absence of aberrant arteries at the site showing sub-lobation), 2) a rat liver showing spontaneously occurring lobar atrophy in the caudate lobe (to compare with histological characteristics in lesions induced by hypoxia possibly due to circulatory disturbance in the portal vein), 3) livers of rats in an acute dermal toxicity study that were subjected to wrapping of the torso once with a bandage applied to the body (to examine the effect of external pressure on the rat liver as a result of wrapping the torso once (S)-3,5-DHPG and to certify (S)-3,5-DHPG the presence or absence of aberrant arteries at the tip of the interlobar fissure) and 4) livers of guinea pigs in a skin sensitization test that were subjected once or multiple times to wrapping of the torso with a bandage applied to the body (to examine the effect of external pressure on the guinea pig liver as a result.