Effects of DMTU on the Expression of Apoptosis in the Liver of Rats after Ischemia and Reperfusion

Kim, Ik Yong; Paik, Doo Jin; Cho, Nam Cheon; Rhoe, Byoung Seon

Abstract

PURPOSE: Prolonged hepatic ischemia followed by reperfusion in surgery or transplantation results in severe cell death. Apoptosis is one type of cell death and occurs under various conditions. Apoptosis differs from necrosis not only morphologically but also in the mediators and mechanism of injury. It has been recently recognized that oxygen-free radicals are major mediators of apoptosis during ischemia/reperfusion. It was reported that pretreatment with a radical scavenger, such as catalase or superoxide dismutase (SOD) attenuated the apoptotic cell death and that old animals showed a higher catalase, SOD, glutatione peroxidase activity in their livers than young rats. This study was designed to characterize the types of cells within the liver and the extent to which those cells undergo apoptosis during ischemia/reperfusion in rats of different ages and to investigate the effect of dimethylthiourea (DMTU), a scanvenger of reactive hydroxyl radicals, on the induction of apoptosis in old rats. METHODS: Young male Sprague-Dawley rats at 5 weeks of age weighing about 200 gm and old rats at 15 weeks of age weighing about 450 gm were subjected to 30-minute ischemia. Liver ischemia was performed by inflow occlusion. Another group of old rats was injected with DMTU before the clamping. The rats were sacrificed immediately and at 1, 3, and 24 hour(s) after reperfusion. The specimens were prepared using in-situ staining for apoptotic cell and bodies by using terminal deoxytransferase-mediated dUTP- biotin nick-end labelling (TUNEL) methods. RESULTS: The number of apoptotic sinusoidal endothelial cells was larger than the number of hepatocytes during ischemia/reperfusion. The apoptosis of hepatocytes significantly increased at 1 hour and at 3 hours in the young group. Although the number of cells in the old group was lower than that in young rats, an increase of TUNEL positive hepatocytes cells was noted at 1 hour. There was significant increase in the DMTU-pretreated old rats until 24 hours afterreperfusion. The number of apoptotic sinusoidal endothelial cells was noticeably higher in DMTU- pretreated old rats than you only defined two groups previously: old and young in the other group. In young rats, but not old rats, an increase of positive sinusoidal endothelial cells was observed at 1 hours after reperfusion. CONCLUSION: These results suggested that old rats have more resistance to ischemia/reperfusion injury than young rats and that DMTU dose not attenuate apoptosis of sinusoidal endothelial cells after ischemia/reperfusion, but dose attenuate apoptosis of hepatocytes in the liver.