THE FATE OF PLASMID DNA AFTER INTRAVENOUS-INJECTION IN MICE - INVOLVEMENT OF SCAVENGER RECEPTORS IN ITS HEPATIC-UPTAKE

Purpose. We examined the stability and disposition characteristics of a naked plasmid DNA pCAT as a model gene after intravenous injection in mice to construct the strategy of in vivo gene delivery systems. Methods. After the injection of pCAT to the mice, stability, tissue distribution, hepatic cellular localization, and effect of some polyanions on the hepatic uptake were studied. Results. The in vitro study demonstrated that the pCAT was rapidly degraded in mouse whole blood with a half-life of approximately 10 min at a concentration of 100 mu g/ml. After intravenous injection, pCAT was degraded at a significantly faster rate than that observed in the whole blood, suggesting that pCAT in vivo was also degraded in other compartments. Following intravenous injection of [P-32] pCAT, radioactivity was rapidly eliminated from the plasma due to extensive uptake by the liver. Hepatic accumulation occurred preferentially in the non-parenchymal cells. The hepatic uptake of radioactivity derived from [P-32] pCAT was inhibited by preceding administration of polyanions such as polyinosinic acid, dextran sulfate, maleylated and succinylated bovine serum albumin but not by polycytidylic acid. These findings indicate that pCAT is taken up by the liver via scavenger receptors on the non-parenchymal cells. Pharmacokinetic analysis revealed that the apparent hepatic uptake clearance was fairly close to the liver plasma flow. Conclusions. These findings provide useful information for the development of delivery systems for in vivo gene therapy.