cis-Platinum: subcellular distribution and binding to cytosolic ligands

Area of Science:

• Pharmacology
• Toxicology
• Biochemistry

Background:

• Cis-diamminedichloroplatinum (cis-DDP) is a widely used chemotherapy drug.
• Understanding its tissue distribution and cellular interactions is crucial for optimizing therapeutic efficacy and minimizing toxicity.

Purpose of the Study:

• To investigate the tissue uptake and subcellular distribution of platinum (Pt) in rat liver and kidneys following cis-DDP administration.
• To examine the binding of Pt to cytosolic ligands and identify key cellular compartments involved.

Main Methods:

• Rats were injected intraperitoneally with cis-diamminedichloroplatinum (cis-DDP) at a dose of 5 mg/kg.
• Tissue uptake and subcellular distribution of Pt were measured in liver and kidney tissues.
• Pt binding to cytosolic ligands was analyzed, including molecular weight and protein binding.

Main Results:

• Platinum (Pt) concentration peaked within 24 hours in both liver and kidney, followed by bimodal clearance.
• In the kidney, high Pt concentrations were observed in microsomal, lysosomal, and mitochondrial fractions; in the liver, higher levels were in microsomal and nuclear fractions.
• A significant portion of cellular Pt (62% in kidney, 89% in liver) localized in the cytosol, with 52% as low molecular weight species at 24 hours. Approximately 25% of cytosolic Pt was bound to a metallothionein-like protein.

Conclusions:

• High cytosolic localization of Pt and a substantial proportion of non-protein-bound species may be critical factors in the therapeutic and toxic effects of cis-DDP.
• These findings provide insights into the pharmacokinetic and pharmacodynamic behavior of cis-DDP at the cellular level.