The tumor distribution and the disposition of serum proteins, such as albumin, fetuin, transferrin, and IgG, were investigated in mice bearing Sarcoma 180. Serum proteins labeled with fluoresceinisothiocyanate (FITC) were administered to the mice. The FITC-labeled proteins acylated with glutaric anhydride were also administered to the mice in order to investigate the effect of chemical modification. The plasma concentration of each glutarylated serum protein was significantly lower, about 15 to 46-fold, in comparison to that of the non-acylated protein at 24 h after administration. The tissue distributions of the glutarylated serum proteins were also decreased compared to those of the non-acylated proteins. Especially, the hepatic distribution of albumin and IgG was significantly reduced with glutarylation. The urinary excretion of albumin and transferrin, and fecal excretion of IgG, were significantly increased with glutarylation. The serum proteins were accumulated effectively in the tumor tissue in mice bearing Sarcoma 180. It was found that the tumor distributions were not impaired by the glutarylation, except involving fetuin. It was suggested, therefore, that the glutarylated serum proteins were valuable for relative tumor-selectivity and might be utilized in a macromolecular carrier system for antitumor drugs.
In order to improve the deposition of mitomycin C (MMC) in the administered site, water-insoluble mitomycin C-albumin conjugate (MMC-G-BSA) was prepared. MMC was covalently attached to the glutarylated bovine serum albumin (G-BSA) in the presence of 1-ethyl-3-(3-dimethyl-aminopropyl) carbodiimide hydrochloride (EDC) to give MMC-G-BSA. The MMC content of the conjugate (16.3% (w/w)) was higher than that of water-soluble mitomycin C-albumin conjugates. MMC was liberated from MMC-G-BSA suspended in a phosphate buffer (pH 7.4, 37 degrees C) with a half-life of 155.3 h. In the same buffer system containing alpha-chymotrypsin, MMC-G-BSA was dissolved perfectly within 24 h due to enzymatic degradation, and the liberation of MMC from the conjugate was significantly accelerated (t1/2 = 24.5 h). After intraperitoneal injection in mice, most of the MMC-G-BSA was retained in the abdominal cavity. Furthermore, the survival time of mice inoculated with Sarcoma 180 was significantly increased by the intraperitoneal injection of MMC-G-BSA. These findings suggest that MMC-G-BSA is a biodegradable macromolecular hybrid which acts as a sustained release delivery system of MMC.
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