A method to study drug concentration-depth profiles in tissues: mitomycin C in dog bladder wall

Area of Science:

• Pharmacology
• Drug Delivery
• Analytical Chemistry

Background:

• Accurate determination of drug concentration-depth profiles is crucial for understanding local drug therapy.
• Evaluating drug transport mechanisms requires precise tissue concentration data.
• A validated method for quantifying drug penetration in biological tissues was lacking.

Purpose of the Study:

• To develop and validate a novel method for determining drug concentration-depth profiles in tissues.
• To quantify the penetration of mitomycin C (MMC) in the canine bladder wall following intravesical instillation.
• To investigate factors influencing drug concentration measurements, such as standardization and tissue processing time.

Main Methods:

• Developed a method involving cryosectioning of tissue into 40-micron segments.
• Employed drug extraction followed by high-pressure liquid chromatography (HPLC) for quantification.
• Validated sensitivity at 1 ng/sample (20 ng/g) for tissue samples.

Main Results:

• Successfully determined mitomycin C (MMC) penetration profiles in the dog bladder wall.
• Standardization to tissue weight provided a better fit for concentration-depth profiles than standardization to protein content.
• A significant decrease in MMC concentration (2- to 10-fold) was observed at the urothelial surface in samples processed after a delay, not attributable to in situ metabolism.

Conclusions:

• The developed method enables accurate quantification of drug penetration in tissues.
• Tissue processing time post-harvesting significantly impacts measured drug concentrations, particularly at the tissue surface.
• Understanding these factors is vital for optimizing local drug delivery strategies and interpreting pharmacokinetic data.