Hepatic Disposition of Cyclosporine A in Isolated Perfused Rat Livers

PURPOSE. To develop an isolated perfused rat liver model to study the hepatic disposition of cyclosporine A (CyA) in both sexes. METHODS. Livers were isolated from male (n = 6) and female (n = 7) rats and perfused with a physiological buffer in a single-pass manner. A bolus 1-mg dose of CyA was injected into the inlet catheter and periodical samples (0-15 min) were collected from the outlet perfusate. The concentrations of CyA in the outlet perfusate, collected bile (0-15 min), and liver tissue (at the end of perfusion) were quantitated by HPLC and subjected to statistical moment analysis. RESULTS. The dilution curves of CyA in the outlet perfusate exhibited unusually long terminal phases due to large volume of distribution of the drug (~100 mL/g) and its slow release from binding sites in the liver (net release rate constant of ~0.020 min-1 ). This was in contrast to the rapid uptake of the drug, indicated by significant amounts of the intact drug (\u3e40%) taken up during one single pass through the liver. Consequently, the liver tissue:perfusate distribution ratio of CyA was very high (~220). No significant differences were found between the male and female livers in any of the estimated parameters. CONCLUSIONS. The tissue binding of cyclosporine A is substantial, slowly reversible, and gender-independent in isolated perfused rat livers

Effects of Methylprednisolone and Its Liver-Targeted Dextran Prodrug on Ischemia–Reperfusion Injury in a Rat Liver Transplantation Model

Purpose. To evaluate the effectiveness of a liver-targeted dextran prodrug (DMP) of methylprednisolone ( MP) in cold preservation-warm reperfusion injury associated with liver transplantation. Methods. The effects of donor pretreatment with single 5 mg/kg doses of MP or DMP on ischemia reperfusion damage to the liver were studied after 8 or 24 h of cold preservation in both isolated perfused rat liver (IPRL) and syngeneic orthotopic rat liver transplantation (OLT) models. Results. In IPRL studies, donor pretreatment with DMP, and to a lesser degree MP, significantly improved the uptake of hyaluronic acid (HA), a marker of endothelial cell function, following 8 h of cold preservation. However, neither pretreatment was protective after 24 h of preservation. In the OLT model using 24-h-preserved livers, the seven-day survival of untreated grafts was 50%. DMP pretreatment of donors significantly improved graft survival to 100%, whereas MP pretreatment was ineffective. Additionally, only DMP significantly increased the blood glucose concentrations and decreased the plasma concentrations of tumor necrosis factor-alpha after OLT. Other measured markers of liver injury were not affected by either pretreatment. Conclusions. Selective delivery of methylprednisolone to the liver as a donor pretreatment strategy improves 24-h preserved graft survival in the OLT model

Attenuation of Acute Rejection in a Rat Liver Transplantation Model by a Liver-Targeted Dextran Prodrug of Methylprednisolone

Background. The use of methylprednisolone (MP) and other corticosteroids for the treatment of acute liver allograft rejection is associated with severe toxicities in nontarget tissues. Therefore, selective delivery of NIP to the liver may improve its efficacy and alleviate its side effects. We investigated the effects of a novel liver-targeted dextran prodrug of MP (DMP) in an orthotopic rat liver transplantation (OLT) model. Methods. The model consisted of a high responder rejection strain combination (Dark Agouti donors and Lewis recipients). Liver recipients were intravenously administered saline or a single subtherapeutic dose of MP (5 mg/kg) as the parent drug (MP) or its prodrug (DMP). Different groups were then monitored for graft survival or euthanized 5 or 9 days posttransplantation. Plasma chemistry, including alkaline phosphatase and bilirubin, allograft histology, and survival duration were determined. Results. Untreated recipients exhibited elevated plasma levels of liver injury markers, progressive portal and venous inflammation and cellular infiltration in liver allografts, and a mean graft survival time (MST) of 10.5 days. MP treatment did not alter any of these parameters. In contrast, a single dose of DMP resulted in a decrease in plasma levels of liver injury markers, a decrease in histological grade of rejection on day 5, and a substantial increase in MST (27.5 days). Conclusions. These results demonstrate attenuation of acute rejection following local (allograft) immunosuppression with a single subtherapeutic dose of NIP delivered as a liver-targeted prodrug. Dextran prodrugs may be useful for selective delivery of immunosuppressants to the liver following liver transplantation

Attenuation of Acute Rejection in a Rat Liver Transplantation Model by a Liver-Targeted Dextran Prodrug of Methylprednisolone

The use of methylprednisolone (MP) and other corticosteroids for the treatment of acute liver allograft rejection is associated with severe toxicities in non-target tissues. Therefore, selective delivery of MP to the liver may improve its efficacy and alleviate its side effects. We investigated the effects of a novel liver-targeted dextran prodrug of MP (DMP) in an orthotopic rat liver transplantation (OLT) model