The role of lipoproteins in the distribution of tin etiopurpurin (SnET2) in the tumor-bearing rat.

The role of plasma lipoproteins in the distribution of the photosensitizing agent tin etiopurpurin (SnET2) was examined in male rats bearing the N-[4-(5-nitro-2-furyl)-2- thiazolyl1bdformamide-induced tumor. Treatment with 17 alpha-ethinyl estradiol resulted in the depletion of total plasma cholesterol by > 70% and a corresponding decrease in plasma lipoproteins. To both control and estradiol-treated animals, a therapeutic dose (1.5 mg/kg) of SnET2 was administered and biodistribution measured 24 h later. Estradiol treatment was not associated with differences in the distribution of SnET2 to liver, skin or tumor, or in the pattern of affinity of SnET2 to plasma albumin and lipoprotein. These results indicate that a substantial decrease in circulating lipoprotein levels does not alter patterns of SnET2 biodistribution.