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Using a fiver perfusion apparatus which was developed in the frame of the Federal Ministry of Education and Research (BMBF) funded project "Physiologic hemoperfusion of isolated organs and its use as a replacement of animal experiments% 18 porcine livers were isolated and normothermic autologously hemoperfused.In the present thesis, this model was applied for toxicological and pharmacological studies for the first time.Two substances were used to examine the toxicological and pharmacological effects: Polidocanol, which is used in human medicine for treatment of varicose veins, and diclofenac a non-steroidal antiphlogistic analgetic drug which frequently used for the treatment of acute pain.The main purpose of this study was to examine ischemia-related, reperfusion-related and substance-induced histological changes of the perfused porcine livers.6 livers which were not treated with substances were used as a control. Two groups consisting of 6 fivers each were subjected to polidocanol or diclofenac which were administered as a bolus.The control group livers were perfused during a period of 180 min. The fivers of the polidocanol-group were perfused for 180 min including a warm-up perfusion period of 30 min. The diclofenac-group was perfused for 240 min including a warm-up of 60 min.The livers were harvested in a commercial abattoir from White German landrace pigs with a mean weight of 85,77 ± 9,37 kg. After electrical stunning, desanguination was started within 30 s by dissection of the neck vessels and blood was collected.After a warm ischemia period of 18,08 ± 7,38 min, lasting from the start of blood collection to the beginning of cold preservation, the livers were weighed.For transport to the laboratory, the organs were perfused with 4°C Euro-Collins-solution. The cold storage period, lasting from the start of cold preservation to beginning of the warm rinsing perfusion with 37°C Ringer-Lactate solution, was 170,23 ± 15,40 min. After warm rinsing, the perfusion with autologous normothermic blood started. The cannulated A. hepatica, V. portae and V. cava caudalis were connected to an extracorporal circulation system. The fiver perfusion system consisted of a blood and a dialysis circuit. The blood was pumped by a pulsatile pump from the reservoir through three parallel fiber dialyse modules into the portal vein and the hepatic artery.After termination of hemoperfusion, the livers were weighed again and 1cm3 tissue probes were dissected out of the left lobe. The probes were fixed in 4 % formaldehyde and proceeded to hematoxylin-eosin stained tissue sections which were examined by light field microscopy using a modified histological score. This score evaluated passive liver congestion, vacuolic degeneration, necrosis and inflammatory cell infiltration which were defined previously (STEFFEN et al., 1990; SUZUKI et al., 1993, NEUHAUS and BLUMHARDT, 1993). Also, leukocyte circulation was evaluated. A 4 grade-score was applied (score 0 to score 3).The comparison of the control group (X0,5 = 1,00) and the polidocanol-group (xo,5 = 1,67) resulted in a difference in vacuolic degeneration of the hepatocytes, which may be based on hypoxia. In this respect, warm and cold ischemia and inhomogenic perfusion may be primary factors contributing to the cellular changes. In the polidocanol group, the vacuolic fiver degeneration may have also been caused by direct surface-modifying effects of polidocanol.Next to the differences in vacuolic: fiver degeneration, the polidocanol group (x0,5 = 1,31) displayed differences in passive liver congestion if compared to the control group (X0,5 = 1,63). Apart from the congestion due to technical procedures which was present in both groups, the higher degree in the polidocanol group was caused by direct effects of polidocanol on endothelial cells. The higher liver weight increase of the polidocanol group (xo,5917,50 g) in comparison to the control group (xo,s = 182,00 g) underlined these results.The degree of liver cell necrosis was also higher in the polidocanol group (X0,5 = 1,42) if compared to the control group (xo,5 = 1,00). While the single cell death can be attributed to physiologic liver regeneration, clusters of Ever cell necrosis in the polidocanol group were attributed to effects caused by increased congestion and also by direct surfacemodifying effects of polidocanol.There was no significant change in leukocyte circulation between the control (x0,5 = 1,50) and polidocanol group (xo,5 =1,50). On the other hand, the polidocanol group (xo,5 = 1,75) displayed higher amounts of inflammatory cell infiltration if compared o the control group (X0,5 = 1,00).In the diclofenac group (xo,5 = 1,58) necrosis was increased in comparison to the control group (xo,5 =1,00). Small and large clusters of parenchymal fiver cell necrosis in the diclofenac group were attributed to substance"s hepatotoxic properties.Also, the degree of passive fiver congestion (diclofenac group (xo,5 = 1,75 vs. control group (xo,5 = 1,31) and organ weight (diclofenac group (xo,5 = 244,50 g vs. control group (xo,5 = 182,00 g) was increased in the diclofenac organs which was mainly attributed to the different perfusion periods.There were no apparent diffierences in vacuolic fiver degeneration between both groups (control group xo,5 = 1,00 vs. diclofenac group (xo,5 = 1,00).Both, the leukocyte circulation (diclofenac group (xo,5 = 2,00 vs. control group (xo,5 = 1,50) and the degree of inflammatory cell infiltration (diclofenac group (xo,5 = 2,00 vs. control group (xo,5 = 1,00) were elevated in the diclofenac group.The main subclass of inflammatory cells was represented by the group of neutrophilic granulocytes which was increased due to the higher numbers of cell necrosis in the diclofenac group.In conclusion, the present thesis using a perfusion apparatus with isolated and normothermic autologously hemoperfused porcine slaughterhouse fivers demonstrated a valid use of the model for toxicological and pharmacological studies.Using the non-steroidal antiphlogistic analgetic drug diclofenac and polidocanol, which is used for the treatment of varicose veins, ischemia-related, reperfusion-related and substanceinduced histological changes were demonstrated. Although a precise diffierentiation was not possible, ischemia- and reperfusion-related injuries were separated from substance-induced effects.