Disposition of a Polymeric Prodrug of Mitomycin C, Mitomycin C-Dextran Conjugate, in the Perfused Rat Liver

The disposition of a polymeric prodrug of mitomycin C (MMC), mitomycin C-dextran conjugate (MMC-D), was studied in the single-pass perfused rat liver in order to clarify the effect of physico-chemical properties, such as molecular weight and electric charge, on the hepatic uptake of MMC-D. Six types of MMC-D were used: both cationic MMC-D (MMC-Dcat) and anionic MMC-D (MMC-Dan) conjugated with dextran with molecular weights of 10,000, 70,000, and 500,000. Outflow curves were analyzed using statistical moment theory. Remarkable hepatic uptake of MMC-Dcat was observed and the uptake amount increased with an increase in molecular weight (i.e., ~80% of the dose was taken up by the liver during a single passage of the conjugate with a molecular weight of 500,000). Intrinsic clearance (CLint,i) and apparent distribution volume (Vi) also increased as the molecular weight increased. On the other hand, almost 100% of applied MMC-Dan was recovered in the outflow regardless of molecular weight, with almost the same moment parameters as those of the vascular reference substance (VRS),131I-labeled human serum albumin (HSA). In a repeated application, the uptake of MMC-Dcat decreased in a stepwise manner, suggesting a saturation in the hepatic uptake of MMC-Dcat, while the uptake of MMC-Dan was unchanged. The MMC-Dcat pretreatment also affected the uptake of Evans blue (EB) bound to bovine serum albumin (BSA). These results demonstrate that molecular weight and electric charge determine the hepatic disposition of macromolecular prodrugs.